- Email: [email protected]
Effect of passive stretch on reproducibility of hip range of motion measurements
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Effect of Passive Stretch on Reproducibility of Hip Range of Motion Measurements Timo J. Aalto, MD, Olavi Airaksinen, MD, DMSc, Tuomas M. Härkönen, MB, Jari P. Arokoski, MD, DMSc ABSTRACT. Aalto TJ, Airaksinen O, Härkönen TM, Arokoski JP. Effect of passive stretch on reproducibility of hip range of motion measurements. Arch Phys Med Rehabil 2005; 86:549-57. Objective: To examine the intra- and intertester and intraand interday reliability of hip passive range of motion (PROM) measurements and the effect of passive stretch on the reproducibility of PROM measurements. Design: Reliability study. Setting: Rehabilitation clinic at university hospital. Participants: Twenty volunteers (12 women, 8 men; age range, 18 – 45y). Interventions: Not applicable. Main Outcome Measures: Two physical therapists made 2 PROM measurements on the first day and repeated them once after 2 days. The PROM in hip flexion, extension, and inner rotation and knee flexion were determined. The measurements of the hip flexion and inner rotation involved either 1 or 8 short-term passive stretches. The reproducibility was expressed as the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) (in percent). Results: The passive stretch increased significantly (P⬍.05 to P⬍.001) the PROM of the hip joint. The reproducibility of the PROM measurement did not increase after repetitive passive stretch. The intra- and interday intra- and intertester ICC and CV of the PROM of the hip flexion and hip inner rotation ranged from .655 to .988 and 2.1% to 12.6%, respectively. The intra- and intertester intra- and interday ICC of the PROM of the hip extension ranged from .740 to .961, and the CV ranged from ⫺85.5% to 242.6%. The intra- and intertester intra- and interday ICC of the PROM of the knee flexion ranged from .497 to .913, and the CV ranged from 2.5% to 9.9%. Conclusions: Repetitive stretching increased significantly the PROM in hip flexion and inner rotation, but the reproducibility of the PROM measurement did not improve. The hip flexion and the hip inner rotation PROM measurements had moderate to very high intra- and interday intra- and intertester reliabilities. The reliability of the PROM in hip extension and knee flexion was poor. Key Words: Hip; Range of motion, articular; Rehabilitation; Reproducibility of results. © 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Department of Physical Medicine and Rehabilitation, Kuopio University Hospital (Aalto, Airaksinen, Arokoski); Kuopio University (Arokoski), Kuopio; Imatra Health Center (Härkönen), Imatra, Finland. Supported by EVO (grant no. 5964012) from Kuopio University Hospital. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Timo J. Aalto, MD, Dept of the Physical Medicine and Rehabilitation, Kuopio University Hospital, PO Box 1777, FIN 70211 Kuopio, Finland, e-mail: [email protected]. 0003-9993/05/8603-9227$30.00/0 doi:10.1016/j.apmr.2004.04.041
IP RANGE OF MOTION (ROM) measurements have H been used to study the effects of physiotherapy on low back pain (LBP), stretching in sports training, and in scores 1
2-4
5,6
evaluating the results of hip surgery. Hip ROM measurements have also been used as a diagnostic test for LBP (straight-leg raising [SLR] test)7 and as a diagnostic aid in hip osteoarthritis.8,9 However, there is no universally accepted standard device for measuring hip ROM.10 In clinical practice, the goniometer has been used to measure ROM. The reliability of the goniometer itself is good, and reproducibility is better during the same measurement session than between 2 measurement sessions.11 Intratester reliability is also considered more reliable than intertester reliability.11 In general, hip flexion ROM has been measured with the knee in the flexed position12 or by using the SLR test.7,13-15 By using the 2-arm goniometer, the intraobserver (but not the interobserver) reproducibility of hip ROM with the knee in flexed position has been good.9,16 SLR measures movement in the hip joint and also hamstring tightness.11 Different instruments and measurement protocols have been used to assess SLR and its reliability and validity.7,13,14,17-20 Although the intra- and intertester and intra- and interday reliabilities have been shown to be good,13,14,19 there is no standard SLR procedure.7 However, in many earlier reliability studies, extensive fixation and instrumentation were used,13,14,19 which may not be practical in the daily clinical routine. Few studies have evaluated the reproducibility of ROM measurement of hip in rotation and extension movements by using the 2-arm goniometer. Croft et al21 showed that intraday measurement of flexion ROM at the hip is repeatable between practitioners, using a plurimeter with the subject in the supine position. By using the Leighton22 flexometer, Ekstrand et al19 reported good intra- and intertester reliabilities in hip extension measurements. They determined hip extension by using the Thomas test, which has been used to assess limited hip extension and hip flexor contracture.23 Bierma-Zeinstra et al16 compared the intra- and intertester reliability of measurements of hip joint motions obtained with an electronic inclinometer and a 2-arm goniometer. They reported that with respect to hip rotation and extension movements, the 2-arm goniometer is accurate when used by a single observer only. However, because it is quite likely the measurements may be taken on a patient serially over time, and possibly by more than 1 physical therapist, the intra- and intertester and intra- and interdays reliabilities of these measurements must be known. ROM of the knee is generally studied as proposed in medical textbooks.12 Knee ROM and stretch ability of the rectus femoris have been studied by using an electronic goniometer and a parallelogram and a 2-arm goniometer.24,25 The parallelogram and a 2-arm goniometer seems to give reliable and valid measurements of knee flexion.25-29 The reliability of measurements may be influenced by changes in ROM that result from repeated testing trials.11 Earlier findings suggest that from 5 to 30 seconds is sufficient time to sustain a hamstring muscle stretch to increase ROM.30-32 Atha and Wheatley33 showed that repeated passive SLR over the first 4 to 5 trials increased the angle of the SLR Arch Phys Med Rehabil Vol 86, March 2005
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test when measured on the same day. Although it has been suggested that using the means of multiple measurements improves reliability,34 other studies indicate that this procedure never improves the reliability of ROM measurements.35,36 As far as we are aware, there are no published studies on the effect of passive stretch on intertester and interday reliability of hip joint ROM. Our purpose in this study was to estimate intra- and intertester reproducibility with intra- and interday (2d) reproducibility of passive ROM (PROM) measurements of hip flexion, hip extension, hip inner rotation, and knee flexion by using the 2-arm (universal) goniometer. The measurement techniques for PROM were those that are used in clinical practice by physical therapists and physicians, with no special fixation of the pelvis or lower extremities and no assistance or elaborate equipment. The hypothesis was that intratester and intraday reproducibility of PROM measurement would be better than intertester and interday reproducibility. Second, we studied the effects of repeated stretching on the reliability of PROM measurements. We hypothesized that repetitive stretching would increase PROM and the reproducibility of PROM measurements. METHODS Participants Twenty students (12 women, 8 men), aged 18 to 45 years (mean, 23.3y), were selected. The subjects were from 157.5 to 185cm (mean ⫾ standard deviation [SD], 172.9⫾7.2cm) in height and 51.8 to 88.5kg (mean, 67.4⫾11.0kg) in weight. Subjects were excluded if they had any of the following diagnoses, symptoms, or medications: rheumatoid arthritis, polyneuropathia, neuromuscular disorders, atherosclerosis of lower extremities, painful hip or knee, previous back surgery, or painful back. A 1-month leisure time physical activity history was recorded for each subject. The histories showed that 5% of the subjects had done no leisure time physical activity in the past month, 40% participated in physical exercise (eg, walking, jogging, skiing, bicycling, swimming) 1 to 2 times a week, and 55% exercised 3 to 5 times a week. Participants were asked not to engage in moderate, heavy, or unusual sports activity for 48 hours before the start of the study, and they were informed that the current protocol had been approved by the Ethics Committee of the Kuopio University Hospital. PROM Measurements The PROM of hip flexion, extension, and hip inner rotation and knee flexion were determined bilaterally by using a masked 2-arm goniometer (fig 1– 4). There was no warmup period. Environmental influences were standardized by taking the measurements at the same time of day and at room temperature. A subject’s right side was measured first. When the measurement was complete, the observer (TMH) locked the goniometer and recorded the result. It was then unlocked and given back to the physical therapist. Two well-trained physical therapists examined the subjects over 3 weeks, 4 volunteers per day. On the first day (Monday or Tuesday), physical therapist A measured the subject twice (M1, first measurement session; M2, second measurement session) (fig 5). Then therapist B also measured the subjects twice (M3, third measurement session; M4, fourth measurement session). Thus, 1 volunteer was measured 4 times on the first day. Measurements of the hip flexion and hip inner rotation involved 8 short-term (1–2s) passive stretches during each measurement session; consequently, the total sum of passive stretches was 32 per side. The time between measurements Arch Phys Med Rehabil Vol 86, March 2005
Fig 1. Measurement of the passive hip flexion for (A) starting position and (B) end position. See Methods for details.
sessions was a minimum of 15 minutes. Physical therapist A or B remeasured each patient once after 48 hours (M5A⫽therapist A [n⫽8]; M5B⫽therapist B [n⫽12]). The passive movement, including stretching, was done until the firm (or bony) end was reached and/or discomfort limited
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therapist measured the angle between femur and tibia with the left knee still passive maximally flexed. Hip inner rotation. The subject was in a sitting position, hands placed on the pelvis21 (figs 4A, 4B). The flexor sides of the knees were near the edge of the examination table, with the calves hanging freely. The goniometer was placed on the tuberositas tibiae. One arm hung freely, and the stationary arm was placed toward the center of the talocrural articular space. The internal rotation of the femur was carried out by bending the calf laterally, with the knee at 90° of flexion, until either muscle resistance or the bony end was reached. The angle between the vertical line and tibia was recorded. Statistical Analysis SPSS, version 10.1.3,a for Windows was used for statistical analysis. Normalities of distributions were tested with 1-sample Kolmogorov-Smirnov test. To detect differences between 2 measurements, averages of PROM paired t tests were used. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) (in percent) were calculated to describe reproducibility. P less than .05 was considered to be statistically significant. Fig 2. Measurement of the passive hip extension. See Methods for details.
the motion or compensatory movement occurred. A total of 8 repetitive stretches were made. The height of the examination table was not standardized and no drawing ink landmarks were used. The measurement order was always the same (hip flexion, hip extension, knee flexion, hip inner rotation), as follows. Hip flexion (modified version of the SLR test7). The subject was in the supine position (fig 1). The center of the goniometer was placed on the trochanter major, with 1 arm limp and the stationary arm placed parallel to the femur toward the center of the tibiofemoral articular space. With the knee at extension, talocrural articulation not fixed, the therapist flexed the hip with 1 hand holding the calf at the level of the malleolus and the goniometer held in place with the other hand. The angles between the horizontal level and the femur after the first and then after the eighth stretch were recorded. Hip extension (modified version of the Thomas test23). The subject was supine (fig 2). The physical therapist pulled volunteers to the edge with a towel so that the ischial tuberosities were at the same vertical line as the edge of the table. The left hip was flexed as far as possible, with the volunteer holding the knee against the chest with both hands. No passive stretches were performed. The measured thigh hung freely, and the center of the goniometer was placed on the trochanter major. One arm of the goniometer was placed parallel to the horizontal level, and the stationary arm was adjusted to the center of the tibiofemoral articular space. The knee joint also hung loosely. The angle of the femur and horizontal levels was measured. If the stationary arm remained above the horizontal level, the angle was marked as negative. If the arm was beneath the horizontal level, the angle was marked as positive. Then, with the left knee still fixed, the next estimation and measurements of the rectus femoris muscle were done on the right side. Knee flexion. The subject was in the supine position, holding the left hip flexed as in the Thomas test23 (fig 3). The goniometer was placed on the center of the lateral tibiofemoral articular space, and 1 arm was placed toward the lateral malleolus, with the other toward the trochanter major. The physical
RESULTS Repeated Stretching and PROM The ICC and CV of passive hip flexion and inner rotation ROM between the first and the eighth stretch were .875 to .985 and 2.5% to 9.9%, respectively (table 1). Although the PROM
Fig 3. Measurement of the passive knee flexion. See Methods for details.
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Fig 4. Measurement of the passive hip inner rotation (A) starting position and (B) end position. See Methods for details.
ICC values were good or excellent during a single measurement session, passive stretching significantly increased PROM of the hip joint (table 1). The significant positive difference between means of the eighth and the first stretch ranged between 2.3° to 7.9°. In general, the reproducibility of the PROM measurement was not increased (tables 2–5) when the results of the first and eighth PROM measurements were compared.
CVs of the PROM of the knee flexion were good (range, 4.5%– 8.8%), ICC values were as low as .516. After 48 hours, the mean values of the PROM of the hip flexion were significantly higher with physical therapist A (right side) and lower with physical therapist B. The mean values of the PROM of the knee flexion were significantly higher with physical therapist A but not with physical therapist B.
Intraday Intratester Reliabilities
Interday Intertester Reliabilities The interday intertester reliabilities are shown in table 5. The interday intratester ICC and CV values of the PROM of the hip flexion and hip inner rotation were in the ranges of .749 to .955 and 4.6% to 12.6%, respectively. The CV of the PROM of the hip extension was very high (range, ⫺85.5% to 58.8%). Although CVs of the PROM of the knee flexion were good (range, 8.5%–9.9%), ICC values were as low as .497. The mean values of the PROM of the hip inner rotation (left side) and knee flexion were significantly higher on the second measurement day than on the first one.
The intraday intratester reliabilities are shown in table 2. The intraday intratester reproducibility of the PROM of the hip flexion, hip inner rotation, and knee flexion were good or excellent according to both ICC (range, .813–.982) and CV (range, 2.3%– 8.4%). However, the mean values in some ROMs were slightly, but significantly, higher in the second test situation than in the first. The ICC of the PROM of the hip extension was excellent (range, .918 –.961), but the CV of the PROM of the hip extension was high (⫺9.3% to 29.1%). Intraday Intertester Reliabilities The intraday intertester reliabilities are shown in table 3. The intraday intertester reproducibility of the PROM of the hip flexion and hip inner rotation were good or excellent according to both the ICC (range, .832–.936) and the CV (range, 4.0%– 11.1%) values. The CV of the PROM of the hip extension was very high (range, 79.8 –242.6). Although the CVs of the PROM of the knee flexion were good, ICC values were low (range, .615–.617). The mean values of the PROM of the hip flexion, inner rotation, and knee flexion were significantly higher for therapist B compared with therapist A. Interday Intratester Reliabilities The interday intratester reliabilities are shown in table 4. The interday intratester ICC and CV values of the PROM of the hip flexion and hip inner rotation were in the ranges .655 to .988 and 2.1% to 12.3%, respectively. The CV of the PROM of the hip extension was high (range, ⫺5.6% to 35.0%). Although Arch Phys Med Rehabil Vol 86, March 2005
DISCUSSION Our purpose in this study was to assess goniometric reliability in a clinical setting. To our knowledge, this is the
Fig 5. Measurement protocol. One subject was measured consecutively in the M1 to M4 sessions during the first day by physical therapist A (ThA) and physical therapist B (ThB). Forty-eight hours later therapist A measured 8 patients (M5A) and therapist B measured 12 patients (M5B).
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MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 1: Reproducibility Between the First and the Eighth Stretches Therapist A Parameters
1st Stretch
8th Stretch
Therapist B CV (%)
ICC
1st Stretch
8th Stretch
M1 Hip flexion Right Left Hip inner rotation Right Left Hip flexion/SLR Right Left Hip inner rotation Right Left
97⫾15 98⫾14 46⫾11 47⫾10
100⫾16† 103⫾14‡ 52⫾12‡ 54⫾11‡ M2
CV (%)
ICC
2.5 3.0
.981 .968
8.3 9.2
.957 .930
M3 3.4 3.5
.970 .985
103⫾14 98⫾13
9.5 9.1
.962 .952
51⫾10 53⫾9
105⫾14* 101⫾13† 57⫾11‡ 61⫾10‡ M4
98⫾14 101⫾15
102⫾15† 104⫾15*
2.9 3.8
.975 .959
104⫾16 99⫾13
107⫾15† 102⫾14†
2.8 2.9
.985 .979
49⫾12 50⫾9
55⫾14‡ 56⫾11‡
8.1 6.8
.967 .972
52⫾10 55⫾9
59⫾10‡ 63⫾9‡
9.9 9.4
.917 .875
NOTE. Values are mean ⫾ SD unless otherwise indicated. Abbreviations: M1– 4, measurement sessions 1– 4 (see Methods, fig 5). *P⬍.05. † P⬍.01. ‡ P⬍.001, indicates a significant difference between first stretch and eighth stretch.
first study to evaluate the intra- and intertester reliability of PROM measurements in the hip on separate days and the effects of repetitive stretching on the reproducibility of PROM measurements. Our results show that there are significant differences between intra- and intertester and intraand interday reliability of the different PROM measurements in the hip and knee joints. As hypothesized, passive stretching significantly increased the PROM of hip flexion and inner rotation. The significant positive difference between the means of the eighth and the
first stretch was about 5°. It is possible that the stretching that occurred during previous PROM tests would potentially also increase the PROM for the next tests. This effect of stretching, that is, improvement in PROM, has been demonstrated after short-term stretching and exercise programs.3,33,37,38 Holding the stretch for 15 seconds causes an increase in ROM of the hamstring.37 Magnusson3 showed that a single static stretch resulted in a 30% viscoelastic stress relaxation of muscle. However, although repeated stretches reduced the muscle stiffness, it returned to baseline values within 1 hour.
Table 2: Intraday Intratester Reproducibility of PROM Therapist A Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M2
Therapist B CV (%)
ICC
M3
M4
CV (%)
ICC
97⫾15 98⫾14
98⫾14 101⫾15*
3.6 3.6
.944 .956
103⫾14 98⫾13
104⫾16 99⫾13
2.9 2.2
.960 .976
100⫾16 103⫾14
102⫾15 104⫾15
2.4 3.2
.982 .965
105⫾14 101⫾123
107⫾15* 102⫾14
2.3 3.1
.982 .958
⫺9.3 2.9
.961 .918
7⫾8 10⫾8
10⫾9† 13⫾8†
29.1 25.2
.947 .932
6⫾8 7⫾11
8⫾8 9⫾8
46⫾11 47⫾10
49⫾12* 50⫾9
8.4 7.2
.933 .928
51⫾10 53⫾9
52⫾10 55⫾9†
4.2 4.3
.952 .965
52⫾12 54⫾11
55⫾14 56⫾11
6.9 5.7
.942 .951
57⫾11 61⫾10
59⫾10 63⫾10†
5.1 4.8
.950 .955
118⫾13 120⫾15
123⫾11* 127⫾13†
4.3 4.5
.874 .896
132⫾12 133⫾12
3.3 2.5
.813 .913
134⫾10 134⫾10
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. † P⬍.01, indicates a significant difference between separate measurements.
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MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 3: Intraday Intertester Reproducibility of PROM Therapist A Versus Therapist B Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M3
CV (%)
ICC
97⫾15 98⫾14
103⫾14† 98⫾13
5.2 4.8
.936 .903
100⫾16 103⫾14
105⫾14* 101⫾13
5.5 4.0
.912 .918
79.8 242.6
.860 .877
6⫾8 7⫾11
7⫾8 10⫾8
46⫾11 47⫾10
51⫾10† 53⫾9†
11.1 10.9
.905 .847
52⫾12 54⫾11
57⫾11† 61⫾10†
11.0 10.9
.875 .832
118⫾13 120⫾15
132⫾12‡ 133⫾12†
9.4 8.4
.617 .615
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. P⬍.01. ‡ P⬍.001, indicates a significant difference between separate measurements. †
Our findings suggest that 8 short-term (1–2s) stretches may not be sufficient to improve the PROM maximally and that there might still be an increase in the PROM after a higher number of repetitive stretches. On the other hand, after repetitive 8 stretches, neither intra- and intertester nor intra- and
interday reproducibility of the PROM measurement of hip flexion and inner rotation were clearly better than after the first stretch. In clinical practice, one does not need to do repetitive stretching when evaluating hip PROM. Our study findings, except for the PROM of hip extension, agree with those of previous investigators13,14,16,19 who showed good intratester reliability of hip PROM measurement. For example, by using a similar type of measurement assessment as in our study Ekstrand et al19 found that the hip extension and flexion intratester interday CV values were 7.2% and 4.9%, respectively. Their hip flexion CV values were comparable with ours, but they obtained much lower CV values for hip extension. Our results also agree with the findings of Ellis and Stowe,39 Boone at al,35 Rothstein et al,36 and Watkins et al28 showing that the intratester reliability is greater than the intertester reliability. Ellis and Stowe39 found up to 5% error in their intratester measurements and up to 10% error in intratester measurements of hip PROM. In general, it has been reported that although the ROM measurements with a goniometer permit high intratester reliability, they have poorer intertester reliability.11 Thus, to minimize error in hip PROM measurements, the measurements on each patient should be taken by the same observer. Fredriksen et al13 studied the reliability of a test designed to measure tightness of the hamstring muscles. The knee was passively extended by a standardized force, whereas the hip was stabilized in 120° of flexion. The knee angle, measured with a goniometer, represents the hamstring tightness. The CV of repeated measurements showed a day-to-day variation up to 3.2%. These findings are consistent with our results, although the 2 studies were conducted with different measurement instruments. When the PROM measurements are done on different days, the goniometer method is predicted to yield more variable results, as shown earlier.20,40 In our study, the day-today intra- and intertester reliability was moderate to excellent only for the PROM for hip flexion and inner rotation.
Table 4: Interday Intratester Reproducibility of PROM Therapist A (n⫽8) Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M5
93⫾8 97⫾8
101⫾10* 101⫾8
99⫾10 100⫾9
Therapist B (n⫽12) ICC
M3
M5
6.4 4.8
.785 .655
106⫾17 100⫾15
104⫾17* 96⫾1*
2.6 4.0
.988 .971
103⫾10* 104⫾10
3.0 4.0
.961 .893
107⫾18 101⫾16
105⫾17* 101⫾20
2.1 3.2
.992 .970
4⫾9 3⫾9
7⫾6 6⫾8
26.6 23.6
.939 .934
6⫾8 12⫾8
10⫾8* 12⫾7
⫺5.6 35.0
.927 .884
41⫾10 46⫾12
47⫾13 52⫾12
12.3 10.8
.887 .867
53⫾10 54⫾8
53⫾6 56⫾6
5.0 7.6
.884 .724
46⫾12 51⫾12
52⫾12* 58⫾11†
11.7 10.5
.885 .967
58⫾11 71⫾9
60⫾7 63⫾8
6.2 5.9
.853 .874
8.8 6.4
.596 .855
128⫾13 132⫾13
134⫾10 136⫾8
5.9 4.5
.516 .715
117⫾12 120⫾15
132⫾7† 131⫾8*
CV (%)
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. † P⬍.01, indicates a significant difference between measurements.
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CV (%)
ICC
MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 5: Interday Intertester Reproducibility of PROM Therapist A Versus Therapist B Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M5
CV (%)
ICC
99⫾17 99⫾18
104⫾16 96⫾18
5.7 5.8
.942 .929
101⫾19 104⫾17
105⫾17 101⫾20
5.0 4.6
.955 .952
7⫾8 10⫾11
10⫾8 12⫾7
⫺85.5 58.8
.827 .740
49⫾11 48⫾9
53⫾6 56⫾6*
11.4 12.6
.749 .748
56⫾11 56⫾10
60⫾7 63⫾8*
9.4 10.8
.749 .819
119⫾15 120⫾16
134⫾10* 136⫾8*
8.5 9.9
.602 .497
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.01, indicates a significant difference between measurements.
The reliability of the PROM of hip extension was poor. The Thomas test has been used as the standard for assessment of limited hip extension and hip flexor contracture.23 In the study by Eland et al,23 the angle of hip extension in the gravitydependent position varied from 6.4° to 10.3°. Our results are similar. Unfortunately, the Thomas test represents not only the hip joint, but also the other joints (lumbar spine, sacroiliac, and knee joint) involved in the results obtained with this test. Although the reasons for the poor intertester reliability in the hip extension PROM measurements could not be determined from our study, we think that the effects of other components and the subjects’ position on the examination table significantly contributed to the measurement error. It may be difficult to fix the pelvis always in exactly the same place. The PROM measurement of knee flexion was highly reliable when the same physical therapist took repeated measurements within 1 day. In contrast, the intraday intertester and interday intra- and intertester variation of the PROM measurement of the knee flexion were not clinically acceptable. The reproducibility of knee ROM measurement has been examined before, showing that the goniometric method is also reliable (ICC, .90 –.99) when the measurements are taken with different observers.25-29,41 Based on these previous studies, we would expect that interobserver reliability for the PROM measurements to be high. However, the testing positions differed, which might have had an impact on the reliability. Variations in the PROM measurements are the sum of goniometer (measuring device), intertester (different observers), and interassay (different measurement sessions) errors. The goniometer error was considered to be negligible. Previous work17,24 has shown that differences between pelvic position (tilt) may strongly affect the results.17,24 The physical therapists may have used different patient positioning on the examination table, or their locations for bony landmarks were improper, which might partly explain the low reliability in the hip extension and knee flexion measurements. The results of the PROM measurements are also dependent on the force applied
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during measurement. The changes in PROM may simply be attributable to day-to-day variations in the force applied to the muscle. We believe that the lower interday reliability of the PROM measurement is not simply because of the repetitive stretching. It has been proposed that ICC values can be accepted as clinically meaningful if the ICC is .80 or greater.42 Although many of the ICC values were .80 or higher in this study, using only the ICC provides an overestimation of the degree of reliability. The fact that lower levels of reliability were measured by the CV than in the ICC can be explained by the fact that these 2 statistical techniques do not measure the same thing. The CV is a more accurate measure of variability. It seems that the CV was not always calculated with the ICC in earlier ROM reliability studies. Interpretation of the results is a major problem when the measured angle is very low, a few degrees below or above zero. This means that total error is also low. Mathematically, this means that reproducibility is good because of the minimal absolute variation. However, with the CV, the opposite is the case. Even a 1° error results in a rather high variation. For example, if the first measurement result is ⫹5° and next measurement is ⫹4°, the error is 20%. Accordingly, although the measurement of the hip flexor tightness is mathematically reproducible, the CV must be considered when estimating the results of therapy. However, although we found high ICC and CV values for both intra- and intertester reliability, significant differences were noted when the mean raw data were compared. Our results may partly be systematically attributable to the effect on the PROM of repetitive stretching. Boone and Azen43 postulated that a 6° difference is acceptable in lower-extremity ROM measurements when more than 1 tester is taking the measurements. Our results are similar, suggesting that a difference of about 5° is statistically significant. By using a constant testing pattern, it is the possibile that the results may be influenced by an ordering effect. The influence of repetition of the testing procedure could have been eliminated by changing the testing order, but this was not done for practical reasons. The PROM measurement should be quick and easy for a physician or a physical therapist to carry out. We did not use separate fixing protocols that would have required a major investment of effort because these can rarely be implemented in clinical practice. However, the measurement protocol was well standardized and blinded so that the physical therapist was not allowed to read the results from the goniometer. A rather wide degree in the variability of the normal ROM of hip has been found among healthy subjects.43-47 In Finland, we do not have population-based normal values for the hip and knee PROM by age and sex. Many of our results are similar to earlier publications, although our testing positions differed. The wide variability of normal ROM values may reflect not only the normal variation but also the error associated with the measurement. It is also possible that muscle stretch ability differs from person to person. CONCLUSIONS Repetitive stretching increased the PROM in hip flexion and inner rotation, but the reproducibility of the PROM measurement did not improve. Results of this study indicate that, for the hip flexion and hip inner rotation, knee goniometric PROM measurements are moderately or highly repeatable in clinical use, but that repeated measurements of hip joints should be primarily taken by the same physical therapist. The reliability of the PROM in hip extension and knee flexion is poor, as assessed in the Thomas test position. Arch Phys Med Rehabil Vol 86, March 2005
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Acknowledgments: Special thanks to physiotherapists Paula Immonen, Minna Siitari, and Leena Hersio for practical help and for organizing the measurements. References 1. Kuukkanen T, Malkia E. Effects of a three-month therapeutic exercise programme on flexibility in subjects with low back pain. Physiother Res Int 2000;5:46-61. 2. van Mechelen W, Hlobil H, Zijlstra WP, de Ridder M, Kemper HC. Is range of motion of the hip and ankle joint related to running injuries? A case control study. Int J Sports Med 1992;13: 605-10. 3. Magnusson SP. Passive properties of human skeletal muscle during stretch maneuvers. A review. Scand J Med Sci Sports 1998; 8:65-77. 4. Witvrouw E, Danneels L, Asselman P, Have T, Cambier D. Muscle flexibility as a risk factor for developing muscle injuries in male professional soccer players. A prospective study. Am J Sports Med 2003;31:41-6. 5. Shields RK, Enloe LJ, Evans RE, Smith KB, Steckel SD. Reliability, validity, and responsiveness of functional tests in patients with total joint replacement. Phys Ther 1995;75:169-76. 6. McGrory BJ, Freiberg AA, Shinar AA, Harris WH. Correlation of measured range of hip motion following total hip arthroplasty and responses to a questionnaire. J Arthroplasty 1996;11:565-71. 7. Rebain R, Baxter GD, McDonough S. A systematic review of the passive straight leg raising test as a diagnostic aid for low back pain (1989 to 2000). Spine 2002;27:E388-95. 8. Theiler R, Stucki G, Schutz R, et al. Parametric and nonparametric measures in the assessment of knee and hip osteoarthritis: interobserver reliability and correlation with radiology. Osteoarthritis Cartilage 1996;4:35-42. 9. Arokoski MH, Haara M, Helminen HJ, Arokoski JP. Physical function in men with and without hip osteoarthritis. Arch Phys Med Rehabil 2004;85:574-81. 10. Lea RD, Gerhardt JJ. Range-of-motion measurements. J Bone Joint Surg Am 1995;77:784-98. 11. Gajdosik RL, Bohannon RW. Clinical measurement of range of motion. Review of goniometry emphasizing reliability and validity. Phys Ther 1987;67:1867-72. 12. American Academy of Orthopedic Surgeons. Joint motion: method of measuring and recording. Edinburgh: Churchill Livingstone; 1966. 13. Fredriksen H, Dagfinrud H, Jacobsen V, Maehlum S. Passive knee extension test to measure hamstring muscle tightness. Scand J Med Sci Sports 1997;7:279-82. 14. Gajdosik R, Lusin G. Hamstring muscle tightness. Reliability of an active-knee-extension test. Phys Ther 1983;63:1085-90. 15. Magnusson SP, Simonsen EB, Aagaard P, Gleim GW, McHugh MP, Kjaer M. Viscoelastic response to repeated static stretching in the human hamstring muscle. Scand J Med Sci Sports 1995;5: 342-7. 16. Bierma-Zeinstra SM, Bohnen AM, Ramlal R, Ridderikhoff J, Verhaar JA, Prins A. Comparison between two devices for measuring hip joint motions. Clin Rehabil 1998;12:497-505. 17. Idota H, Yoshida T. Clinical significance of the straight-legraising test. Nippon Seikeigeka Gakkai Zasshi 1991;65:1035-44. 18. Cameron DM, Bohannon RW, Owen SV. Influence of hip position on measurements of the straight leg raise test. J Orthop Sports Phys Ther 1994;19:168-72. 19. Ekstrand J, Wiktorsson M, Oberg B, Gillquist J. Lower extremity goniometric measurements: a study to determine their reliability. Arch Phys Med Rehabil 1982;63:171-5. 20. Hsieh CY, Walker JM, Gillis K. Straight-leg-raising test. Comparison of three instruments. Phys Ther 1983;63:1429-33. Arch Phys Med Rehabil Vol 86, March 2005
21. Croft PR, Nahit ES, Macfarlane GJ, Silman AJ. Interobserver reliability in measuring flexion, internal rotation, and external rotation of the hip using a plurimeter. Ann Rheum Dis 1996;55: 320-3. 22. Leighton JR. Instrument and technic for measurement of range of joint motion. Arch Phys Med Rehabil 1955;36:571-8. 23. Eland DC, Singleton TN, Conaster RR, et al. The “iliacus test”: new information for the evaluation of hip extension dysfunction. J Am Osteopath Assoc 2002;102:130-42. 24. Hamberg J, Bjorklund M, Nordgren B, Sahlstedt B. Stretchability of the rectus femoris muscle: investigation of validity and intratester reliability of two methods including X-ray analysis of pelvic tilt. Arch Phys Med Rehabil 1993;74:263-70. 25. Brosseau L, Tousignant M, Budd J, et al. Intratester and intertester reliability and criterion validity of the parallelogram and universal goniometers for active knee flexion in healthy subjects. Physiother Res Int 1997;2:150-66. 26. Rheault W, Miller M, Nothnagel P, Straessle J, Urban D. Intertester reliability and concurrent validity of fluid-based and universal goniometers for active knee flexion. Phys Ther 1988;68: 1676-8. 27. Gogia PP, Braatz JH, Rose SJ, Norton BJ. Reliability and validity of goniometric measurements at the knee. Phys Ther 1987;67: 192-5. 28. Watkins MA, Riddle DL, Lamb RL, Personius WJ. Reliability of goniometric measurements and visual estimates of knee range of motion obtained in a clinical setting. Phys Ther 1991;71:90-6. 29. Brosseau L, Balmer S, Tousignant M, et al. Intra- and intertester reliability and criterion validity of the parallelogram and universal goniometers for measuring maximum active knee flexion and extension of patients with knee restrictions. Arch Phys Med Rehabil 2001;82:396-402. 30. Roberts JM, Wilson K. Effect of stretching duration on active and passive range of motion in the lower extremity. Br J Sports Med 1999;33:259-63. 31. Borms J, Van Roy P, Santens JP, Haentjens A. Optimal duration of static stretching exercises for improvement of coxo-femoral flexibility. J Sports Sci 1987;5:39-47. 32. Bandy WD, Irion JM, Briggler M. The effect of time and frequency of static stretching on flexibility of the hamstring muscles. Phys Ther 1997;77:1090-6. 33. Atha J, Wheatley DW. The mobilising effects of repeated measurement on hip flexion. Br J Sports Med 1976;10:22-5. 34. Low JL. The reliability of joint measurement. Physiotherapy 1976;62:227-9. 35. Boone DC, Azen SP, Lin CM, Spence C, Baron C, Lee L. Reliability of goniometric measurements. Phys Ther 1978;58: 1355-90. 36. Rothstein JM, Miller PJ, Roettger RF. Goniometric reliability in a clinical setting. Elbow and knee measurements. Phys Ther 1983; 63:1611-5. 37. Gajdosik RL. Effects of static stretching on the maximal length and resistance to passive stretch of short hamstring muscles. J Orthop Sports Phys Ther 1991;14:250-5. 38. Wiemann K, Hahn K. Influences of strength, stretching and circulatory exercises on flexibility parameters of the human hamstrings. Int J Sports Med 1997;18:340-6. 39. Ellis MI, Stowe J. The hip. Clin Rheum Dis 1982;8:655-75. 40. McDowell BC, Hewitt V, Nurse A, Weston T, Baker R. The variability of goniometric measurements in ambulatory children with spastic cerebral palsy. Gait Posture 2000;12:114-21. 41. Barker KL, Lamb SE, Burns M, Simpson AH. Repeatability of goniometer measurements of the knee in patients wearing an Ilizarov external fixator: a clinic-based study. Clin Rehabil 1999; 13:156-63.
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42. Kramer MS, Feinstein AR. Clinical biostatistics LIV. The biostatistics of concordance [published erratum appears in Clin Pharmacol Ther 1989;46:309]. Clin Pharmacol Ther 1981;29:111-23. 43. Boone DC, Azen SP. Normal range of motion of joints in male subjects. J Bone Joint Surg Am 1979;61:756-9. 44. Roaas A, Andersson GB. Normal range of motion of the hip, knee and ankle joints in male subjects, 30-40 years of age. Acta Orthop Scand 1982;53:205-8. 45. Roach KE, Miles TP. Normal hip and knee active range of motion: the relationship to age. Phys Ther 1991;71:656-65.
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46. Escalante A, Lichtenstein MJ, Dhanda R, Cornell JE, Hazuda HP. Determinants of hip and knee flexion range: results from the San Antonio Longitudinal Study of Aging. Arthritis Care Res 1999; 12:8-18. 47. Svenningsen S, Terjesen T, Auflem M, Berg V. Hip motion related to age and sex. Acta Orthop Scand 1989;60:97-100. Supplier a. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.
Arch Phys Med Rehabil Vol 86, March 2005
Effect of Passive Stretch on Reproducibility of Hip Range of Motion Measurements Timo J. Aalto, MD, Olavi Airaksinen, MD, DMSc, Tuomas M. Härkönen, MB, Jari P. Arokoski, MD, DMSc ABSTRACT. Aalto TJ, Airaksinen O, Härkönen TM, Arokoski JP. Effect of passive stretch on reproducibility of hip range of motion measurements. Arch Phys Med Rehabil 2005; 86:549-57. Objective: To examine the intra- and intertester and intraand interday reliability of hip passive range of motion (PROM) measurements and the effect of passive stretch on the reproducibility of PROM measurements. Design: Reliability study. Setting: Rehabilitation clinic at university hospital. Participants: Twenty volunteers (12 women, 8 men; age range, 18 – 45y). Interventions: Not applicable. Main Outcome Measures: Two physical therapists made 2 PROM measurements on the first day and repeated them once after 2 days. The PROM in hip flexion, extension, and inner rotation and knee flexion were determined. The measurements of the hip flexion and inner rotation involved either 1 or 8 short-term passive stretches. The reproducibility was expressed as the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) (in percent). Results: The passive stretch increased significantly (P⬍.05 to P⬍.001) the PROM of the hip joint. The reproducibility of the PROM measurement did not increase after repetitive passive stretch. The intra- and interday intra- and intertester ICC and CV of the PROM of the hip flexion and hip inner rotation ranged from .655 to .988 and 2.1% to 12.6%, respectively. The intra- and intertester intra- and interday ICC of the PROM of the hip extension ranged from .740 to .961, and the CV ranged from ⫺85.5% to 242.6%. The intra- and intertester intra- and interday ICC of the PROM of the knee flexion ranged from .497 to .913, and the CV ranged from 2.5% to 9.9%. Conclusions: Repetitive stretching increased significantly the PROM in hip flexion and inner rotation, but the reproducibility of the PROM measurement did not improve. The hip flexion and the hip inner rotation PROM measurements had moderate to very high intra- and interday intra- and intertester reliabilities. The reliability of the PROM in hip extension and knee flexion was poor. Key Words: Hip; Range of motion, articular; Rehabilitation; Reproducibility of results. © 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
From the Department of Physical Medicine and Rehabilitation, Kuopio University Hospital (Aalto, Airaksinen, Arokoski); Kuopio University (Arokoski), Kuopio; Imatra Health Center (Härkönen), Imatra, Finland. Supported by EVO (grant no. 5964012) from Kuopio University Hospital. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Timo J. Aalto, MD, Dept of the Physical Medicine and Rehabilitation, Kuopio University Hospital, PO Box 1777, FIN 70211 Kuopio, Finland, e-mail: [email protected]. 0003-9993/05/8603-9227$30.00/0 doi:10.1016/j.apmr.2004.04.041
IP RANGE OF MOTION (ROM) measurements have H been used to study the effects of physiotherapy on low back pain (LBP), stretching in sports training, and in scores 1
2-4
5,6
evaluating the results of hip surgery. Hip ROM measurements have also been used as a diagnostic test for LBP (straight-leg raising [SLR] test)7 and as a diagnostic aid in hip osteoarthritis.8,9 However, there is no universally accepted standard device for measuring hip ROM.10 In clinical practice, the goniometer has been used to measure ROM. The reliability of the goniometer itself is good, and reproducibility is better during the same measurement session than between 2 measurement sessions.11 Intratester reliability is also considered more reliable than intertester reliability.11 In general, hip flexion ROM has been measured with the knee in the flexed position12 or by using the SLR test.7,13-15 By using the 2-arm goniometer, the intraobserver (but not the interobserver) reproducibility of hip ROM with the knee in flexed position has been good.9,16 SLR measures movement in the hip joint and also hamstring tightness.11 Different instruments and measurement protocols have been used to assess SLR and its reliability and validity.7,13,14,17-20 Although the intra- and intertester and intra- and interday reliabilities have been shown to be good,13,14,19 there is no standard SLR procedure.7 However, in many earlier reliability studies, extensive fixation and instrumentation were used,13,14,19 which may not be practical in the daily clinical routine. Few studies have evaluated the reproducibility of ROM measurement of hip in rotation and extension movements by using the 2-arm goniometer. Croft et al21 showed that intraday measurement of flexion ROM at the hip is repeatable between practitioners, using a plurimeter with the subject in the supine position. By using the Leighton22 flexometer, Ekstrand et al19 reported good intra- and intertester reliabilities in hip extension measurements. They determined hip extension by using the Thomas test, which has been used to assess limited hip extension and hip flexor contracture.23 Bierma-Zeinstra et al16 compared the intra- and intertester reliability of measurements of hip joint motions obtained with an electronic inclinometer and a 2-arm goniometer. They reported that with respect to hip rotation and extension movements, the 2-arm goniometer is accurate when used by a single observer only. However, because it is quite likely the measurements may be taken on a patient serially over time, and possibly by more than 1 physical therapist, the intra- and intertester and intra- and interdays reliabilities of these measurements must be known. ROM of the knee is generally studied as proposed in medical textbooks.12 Knee ROM and stretch ability of the rectus femoris have been studied by using an electronic goniometer and a parallelogram and a 2-arm goniometer.24,25 The parallelogram and a 2-arm goniometer seems to give reliable and valid measurements of knee flexion.25-29 The reliability of measurements may be influenced by changes in ROM that result from repeated testing trials.11 Earlier findings suggest that from 5 to 30 seconds is sufficient time to sustain a hamstring muscle stretch to increase ROM.30-32 Atha and Wheatley33 showed that repeated passive SLR over the first 4 to 5 trials increased the angle of the SLR Arch Phys Med Rehabil Vol 86, March 2005
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test when measured on the same day. Although it has been suggested that using the means of multiple measurements improves reliability,34 other studies indicate that this procedure never improves the reliability of ROM measurements.35,36 As far as we are aware, there are no published studies on the effect of passive stretch on intertester and interday reliability of hip joint ROM. Our purpose in this study was to estimate intra- and intertester reproducibility with intra- and interday (2d) reproducibility of passive ROM (PROM) measurements of hip flexion, hip extension, hip inner rotation, and knee flexion by using the 2-arm (universal) goniometer. The measurement techniques for PROM were those that are used in clinical practice by physical therapists and physicians, with no special fixation of the pelvis or lower extremities and no assistance or elaborate equipment. The hypothesis was that intratester and intraday reproducibility of PROM measurement would be better than intertester and interday reproducibility. Second, we studied the effects of repeated stretching on the reliability of PROM measurements. We hypothesized that repetitive stretching would increase PROM and the reproducibility of PROM measurements. METHODS Participants Twenty students (12 women, 8 men), aged 18 to 45 years (mean, 23.3y), were selected. The subjects were from 157.5 to 185cm (mean ⫾ standard deviation [SD], 172.9⫾7.2cm) in height and 51.8 to 88.5kg (mean, 67.4⫾11.0kg) in weight. Subjects were excluded if they had any of the following diagnoses, symptoms, or medications: rheumatoid arthritis, polyneuropathia, neuromuscular disorders, atherosclerosis of lower extremities, painful hip or knee, previous back surgery, or painful back. A 1-month leisure time physical activity history was recorded for each subject. The histories showed that 5% of the subjects had done no leisure time physical activity in the past month, 40% participated in physical exercise (eg, walking, jogging, skiing, bicycling, swimming) 1 to 2 times a week, and 55% exercised 3 to 5 times a week. Participants were asked not to engage in moderate, heavy, or unusual sports activity for 48 hours before the start of the study, and they were informed that the current protocol had been approved by the Ethics Committee of the Kuopio University Hospital. PROM Measurements The PROM of hip flexion, extension, and hip inner rotation and knee flexion were determined bilaterally by using a masked 2-arm goniometer (fig 1– 4). There was no warmup period. Environmental influences were standardized by taking the measurements at the same time of day and at room temperature. A subject’s right side was measured first. When the measurement was complete, the observer (TMH) locked the goniometer and recorded the result. It was then unlocked and given back to the physical therapist. Two well-trained physical therapists examined the subjects over 3 weeks, 4 volunteers per day. On the first day (Monday or Tuesday), physical therapist A measured the subject twice (M1, first measurement session; M2, second measurement session) (fig 5). Then therapist B also measured the subjects twice (M3, third measurement session; M4, fourth measurement session). Thus, 1 volunteer was measured 4 times on the first day. Measurements of the hip flexion and hip inner rotation involved 8 short-term (1–2s) passive stretches during each measurement session; consequently, the total sum of passive stretches was 32 per side. The time between measurements Arch Phys Med Rehabil Vol 86, March 2005
Fig 1. Measurement of the passive hip flexion for (A) starting position and (B) end position. See Methods for details.
sessions was a minimum of 15 minutes. Physical therapist A or B remeasured each patient once after 48 hours (M5A⫽therapist A [n⫽8]; M5B⫽therapist B [n⫽12]). The passive movement, including stretching, was done until the firm (or bony) end was reached and/or discomfort limited
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therapist measured the angle between femur and tibia with the left knee still passive maximally flexed. Hip inner rotation. The subject was in a sitting position, hands placed on the pelvis21 (figs 4A, 4B). The flexor sides of the knees were near the edge of the examination table, with the calves hanging freely. The goniometer was placed on the tuberositas tibiae. One arm hung freely, and the stationary arm was placed toward the center of the talocrural articular space. The internal rotation of the femur was carried out by bending the calf laterally, with the knee at 90° of flexion, until either muscle resistance or the bony end was reached. The angle between the vertical line and tibia was recorded. Statistical Analysis SPSS, version 10.1.3,a for Windows was used for statistical analysis. Normalities of distributions were tested with 1-sample Kolmogorov-Smirnov test. To detect differences between 2 measurements, averages of PROM paired t tests were used. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) (in percent) were calculated to describe reproducibility. P less than .05 was considered to be statistically significant. Fig 2. Measurement of the passive hip extension. See Methods for details.
the motion or compensatory movement occurred. A total of 8 repetitive stretches were made. The height of the examination table was not standardized and no drawing ink landmarks were used. The measurement order was always the same (hip flexion, hip extension, knee flexion, hip inner rotation), as follows. Hip flexion (modified version of the SLR test7). The subject was in the supine position (fig 1). The center of the goniometer was placed on the trochanter major, with 1 arm limp and the stationary arm placed parallel to the femur toward the center of the tibiofemoral articular space. With the knee at extension, talocrural articulation not fixed, the therapist flexed the hip with 1 hand holding the calf at the level of the malleolus and the goniometer held in place with the other hand. The angles between the horizontal level and the femur after the first and then after the eighth stretch were recorded. Hip extension (modified version of the Thomas test23). The subject was supine (fig 2). The physical therapist pulled volunteers to the edge with a towel so that the ischial tuberosities were at the same vertical line as the edge of the table. The left hip was flexed as far as possible, with the volunteer holding the knee against the chest with both hands. No passive stretches were performed. The measured thigh hung freely, and the center of the goniometer was placed on the trochanter major. One arm of the goniometer was placed parallel to the horizontal level, and the stationary arm was adjusted to the center of the tibiofemoral articular space. The knee joint also hung loosely. The angle of the femur and horizontal levels was measured. If the stationary arm remained above the horizontal level, the angle was marked as negative. If the arm was beneath the horizontal level, the angle was marked as positive. Then, with the left knee still fixed, the next estimation and measurements of the rectus femoris muscle were done on the right side. Knee flexion. The subject was in the supine position, holding the left hip flexed as in the Thomas test23 (fig 3). The goniometer was placed on the center of the lateral tibiofemoral articular space, and 1 arm was placed toward the lateral malleolus, with the other toward the trochanter major. The physical
RESULTS Repeated Stretching and PROM The ICC and CV of passive hip flexion and inner rotation ROM between the first and the eighth stretch were .875 to .985 and 2.5% to 9.9%, respectively (table 1). Although the PROM
Fig 3. Measurement of the passive knee flexion. See Methods for details.
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Fig 4. Measurement of the passive hip inner rotation (A) starting position and (B) end position. See Methods for details.
ICC values were good or excellent during a single measurement session, passive stretching significantly increased PROM of the hip joint (table 1). The significant positive difference between means of the eighth and the first stretch ranged between 2.3° to 7.9°. In general, the reproducibility of the PROM measurement was not increased (tables 2–5) when the results of the first and eighth PROM measurements were compared.
CVs of the PROM of the knee flexion were good (range, 4.5%– 8.8%), ICC values were as low as .516. After 48 hours, the mean values of the PROM of the hip flexion were significantly higher with physical therapist A (right side) and lower with physical therapist B. The mean values of the PROM of the knee flexion were significantly higher with physical therapist A but not with physical therapist B.
Intraday Intratester Reliabilities
Interday Intertester Reliabilities The interday intertester reliabilities are shown in table 5. The interday intratester ICC and CV values of the PROM of the hip flexion and hip inner rotation were in the ranges of .749 to .955 and 4.6% to 12.6%, respectively. The CV of the PROM of the hip extension was very high (range, ⫺85.5% to 58.8%). Although CVs of the PROM of the knee flexion were good (range, 8.5%–9.9%), ICC values were as low as .497. The mean values of the PROM of the hip inner rotation (left side) and knee flexion were significantly higher on the second measurement day than on the first one.
The intraday intratester reliabilities are shown in table 2. The intraday intratester reproducibility of the PROM of the hip flexion, hip inner rotation, and knee flexion were good or excellent according to both ICC (range, .813–.982) and CV (range, 2.3%– 8.4%). However, the mean values in some ROMs were slightly, but significantly, higher in the second test situation than in the first. The ICC of the PROM of the hip extension was excellent (range, .918 –.961), but the CV of the PROM of the hip extension was high (⫺9.3% to 29.1%). Intraday Intertester Reliabilities The intraday intertester reliabilities are shown in table 3. The intraday intertester reproducibility of the PROM of the hip flexion and hip inner rotation were good or excellent according to both the ICC (range, .832–.936) and the CV (range, 4.0%– 11.1%) values. The CV of the PROM of the hip extension was very high (range, 79.8 –242.6). Although the CVs of the PROM of the knee flexion were good, ICC values were low (range, .615–.617). The mean values of the PROM of the hip flexion, inner rotation, and knee flexion were significantly higher for therapist B compared with therapist A. Interday Intratester Reliabilities The interday intratester reliabilities are shown in table 4. The interday intratester ICC and CV values of the PROM of the hip flexion and hip inner rotation were in the ranges .655 to .988 and 2.1% to 12.3%, respectively. The CV of the PROM of the hip extension was high (range, ⫺5.6% to 35.0%). Although Arch Phys Med Rehabil Vol 86, March 2005
DISCUSSION Our purpose in this study was to assess goniometric reliability in a clinical setting. To our knowledge, this is the
Fig 5. Measurement protocol. One subject was measured consecutively in the M1 to M4 sessions during the first day by physical therapist A (ThA) and physical therapist B (ThB). Forty-eight hours later therapist A measured 8 patients (M5A) and therapist B measured 12 patients (M5B).
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MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 1: Reproducibility Between the First and the Eighth Stretches Therapist A Parameters
1st Stretch
8th Stretch
Therapist B CV (%)
ICC
1st Stretch
8th Stretch
M1 Hip flexion Right Left Hip inner rotation Right Left Hip flexion/SLR Right Left Hip inner rotation Right Left
97⫾15 98⫾14 46⫾11 47⫾10
100⫾16† 103⫾14‡ 52⫾12‡ 54⫾11‡ M2
CV (%)
ICC
2.5 3.0
.981 .968
8.3 9.2
.957 .930
M3 3.4 3.5
.970 .985
103⫾14 98⫾13
9.5 9.1
.962 .952
51⫾10 53⫾9
105⫾14* 101⫾13† 57⫾11‡ 61⫾10‡ M4
98⫾14 101⫾15
102⫾15† 104⫾15*
2.9 3.8
.975 .959
104⫾16 99⫾13
107⫾15† 102⫾14†
2.8 2.9
.985 .979
49⫾12 50⫾9
55⫾14‡ 56⫾11‡
8.1 6.8
.967 .972
52⫾10 55⫾9
59⫾10‡ 63⫾9‡
9.9 9.4
.917 .875
NOTE. Values are mean ⫾ SD unless otherwise indicated. Abbreviations: M1– 4, measurement sessions 1– 4 (see Methods, fig 5). *P⬍.05. † P⬍.01. ‡ P⬍.001, indicates a significant difference between first stretch and eighth stretch.
first study to evaluate the intra- and intertester reliability of PROM measurements in the hip on separate days and the effects of repetitive stretching on the reproducibility of PROM measurements. Our results show that there are significant differences between intra- and intertester and intraand interday reliability of the different PROM measurements in the hip and knee joints. As hypothesized, passive stretching significantly increased the PROM of hip flexion and inner rotation. The significant positive difference between the means of the eighth and the
first stretch was about 5°. It is possible that the stretching that occurred during previous PROM tests would potentially also increase the PROM for the next tests. This effect of stretching, that is, improvement in PROM, has been demonstrated after short-term stretching and exercise programs.3,33,37,38 Holding the stretch for 15 seconds causes an increase in ROM of the hamstring.37 Magnusson3 showed that a single static stretch resulted in a 30% viscoelastic stress relaxation of muscle. However, although repeated stretches reduced the muscle stiffness, it returned to baseline values within 1 hour.
Table 2: Intraday Intratester Reproducibility of PROM Therapist A Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M2
Therapist B CV (%)
ICC
M3
M4
CV (%)
ICC
97⫾15 98⫾14
98⫾14 101⫾15*
3.6 3.6
.944 .956
103⫾14 98⫾13
104⫾16 99⫾13
2.9 2.2
.960 .976
100⫾16 103⫾14
102⫾15 104⫾15
2.4 3.2
.982 .965
105⫾14 101⫾123
107⫾15* 102⫾14
2.3 3.1
.982 .958
⫺9.3 2.9
.961 .918
7⫾8 10⫾8
10⫾9† 13⫾8†
29.1 25.2
.947 .932
6⫾8 7⫾11
8⫾8 9⫾8
46⫾11 47⫾10
49⫾12* 50⫾9
8.4 7.2
.933 .928
51⫾10 53⫾9
52⫾10 55⫾9†
4.2 4.3
.952 .965
52⫾12 54⫾11
55⫾14 56⫾11
6.9 5.7
.942 .951
57⫾11 61⫾10
59⫾10 63⫾10†
5.1 4.8
.950 .955
118⫾13 120⫾15
123⫾11* 127⫾13†
4.3 4.5
.874 .896
132⫾12 133⫾12
3.3 2.5
.813 .913
134⫾10 134⫾10
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. † P⬍.01, indicates a significant difference between separate measurements.
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MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 3: Intraday Intertester Reproducibility of PROM Therapist A Versus Therapist B Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M3
CV (%)
ICC
97⫾15 98⫾14
103⫾14† 98⫾13
5.2 4.8
.936 .903
100⫾16 103⫾14
105⫾14* 101⫾13
5.5 4.0
.912 .918
79.8 242.6
.860 .877
6⫾8 7⫾11
7⫾8 10⫾8
46⫾11 47⫾10
51⫾10† 53⫾9†
11.1 10.9
.905 .847
52⫾12 54⫾11
57⫾11† 61⫾10†
11.0 10.9
.875 .832
118⫾13 120⫾15
132⫾12‡ 133⫾12†
9.4 8.4
.617 .615
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. P⬍.01. ‡ P⬍.001, indicates a significant difference between separate measurements. †
Our findings suggest that 8 short-term (1–2s) stretches may not be sufficient to improve the PROM maximally and that there might still be an increase in the PROM after a higher number of repetitive stretches. On the other hand, after repetitive 8 stretches, neither intra- and intertester nor intra- and
interday reproducibility of the PROM measurement of hip flexion and inner rotation were clearly better than after the first stretch. In clinical practice, one does not need to do repetitive stretching when evaluating hip PROM. Our study findings, except for the PROM of hip extension, agree with those of previous investigators13,14,16,19 who showed good intratester reliability of hip PROM measurement. For example, by using a similar type of measurement assessment as in our study Ekstrand et al19 found that the hip extension and flexion intratester interday CV values were 7.2% and 4.9%, respectively. Their hip flexion CV values were comparable with ours, but they obtained much lower CV values for hip extension. Our results also agree with the findings of Ellis and Stowe,39 Boone at al,35 Rothstein et al,36 and Watkins et al28 showing that the intratester reliability is greater than the intertester reliability. Ellis and Stowe39 found up to 5% error in their intratester measurements and up to 10% error in intratester measurements of hip PROM. In general, it has been reported that although the ROM measurements with a goniometer permit high intratester reliability, they have poorer intertester reliability.11 Thus, to minimize error in hip PROM measurements, the measurements on each patient should be taken by the same observer. Fredriksen et al13 studied the reliability of a test designed to measure tightness of the hamstring muscles. The knee was passively extended by a standardized force, whereas the hip was stabilized in 120° of flexion. The knee angle, measured with a goniometer, represents the hamstring tightness. The CV of repeated measurements showed a day-to-day variation up to 3.2%. These findings are consistent with our results, although the 2 studies were conducted with different measurement instruments. When the PROM measurements are done on different days, the goniometer method is predicted to yield more variable results, as shown earlier.20,40 In our study, the day-today intra- and intertester reliability was moderate to excellent only for the PROM for hip flexion and inner rotation.
Table 4: Interday Intratester Reproducibility of PROM Therapist A (n⫽8) Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M5
93⫾8 97⫾8
101⫾10* 101⫾8
99⫾10 100⫾9
Therapist B (n⫽12) ICC
M3
M5
6.4 4.8
.785 .655
106⫾17 100⫾15
104⫾17* 96⫾1*
2.6 4.0
.988 .971
103⫾10* 104⫾10
3.0 4.0
.961 .893
107⫾18 101⫾16
105⫾17* 101⫾20
2.1 3.2
.992 .970
4⫾9 3⫾9
7⫾6 6⫾8
26.6 23.6
.939 .934
6⫾8 12⫾8
10⫾8* 12⫾7
⫺5.6 35.0
.927 .884
41⫾10 46⫾12
47⫾13 52⫾12
12.3 10.8
.887 .867
53⫾10 54⫾8
53⫾6 56⫾6
5.0 7.6
.884 .724
46⫾12 51⫾12
52⫾12* 58⫾11†
11.7 10.5
.885 .967
58⫾11 71⫾9
60⫾7 63⫾8
6.2 5.9
.853 .874
8.8 6.4
.596 .855
128⫾13 132⫾13
134⫾10 136⫾8
5.9 4.5
.516 .715
117⫾12 120⫾15
132⫾7† 131⫾8*
CV (%)
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.05. † P⬍.01, indicates a significant difference between measurements.
Arch Phys Med Rehabil Vol 86, March 2005
CV (%)
ICC
MEASUREMENT OF THE HIP RANGE OF MOTION, Aalto Table 5: Interday Intertester Reproducibility of PROM Therapist A Versus Therapist B Parameters
Hip flexion 1st stretch Right Left 8th stretch Right Left Hip extension Right Left Hip inner rotation 1st stretch Right Left 8th stretch Right Left Knee flexion Right Left
M1
M5
CV (%)
ICC
99⫾17 99⫾18
104⫾16 96⫾18
5.7 5.8
.942 .929
101⫾19 104⫾17
105⫾17 101⫾20
5.0 4.6
.955 .952
7⫾8 10⫾11
10⫾8 12⫾7
⫺85.5 58.8
.827 .740
49⫾11 48⫾9
53⫾6 56⫾6*
11.4 12.6
.749 .748
56⫾11 56⫾10
60⫾7 63⫾8*
9.4 10.8
.749 .819
119⫾15 120⫾16
134⫾10* 136⫾8*
8.5 9.9
.602 .497
NOTE. Values are mean ⫾ SD unless otherwise indicated. *P⬍.01, indicates a significant difference between measurements.
The reliability of the PROM of hip extension was poor. The Thomas test has been used as the standard for assessment of limited hip extension and hip flexor contracture.23 In the study by Eland et al,23 the angle of hip extension in the gravitydependent position varied from 6.4° to 10.3°. Our results are similar. Unfortunately, the Thomas test represents not only the hip joint, but also the other joints (lumbar spine, sacroiliac, and knee joint) involved in the results obtained with this test. Although the reasons for the poor intertester reliability in the hip extension PROM measurements could not be determined from our study, we think that the effects of other components and the subjects’ position on the examination table significantly contributed to the measurement error. It may be difficult to fix the pelvis always in exactly the same place. The PROM measurement of knee flexion was highly reliable when the same physical therapist took repeated measurements within 1 day. In contrast, the intraday intertester and interday intra- and intertester variation of the PROM measurement of the knee flexion were not clinically acceptable. The reproducibility of knee ROM measurement has been examined before, showing that the goniometric method is also reliable (ICC, .90 –.99) when the measurements are taken with different observers.25-29,41 Based on these previous studies, we would expect that interobserver reliability for the PROM measurements to be high. However, the testing positions differed, which might have had an impact on the reliability. Variations in the PROM measurements are the sum of goniometer (measuring device), intertester (different observers), and interassay (different measurement sessions) errors. The goniometer error was considered to be negligible. Previous work17,24 has shown that differences between pelvic position (tilt) may strongly affect the results.17,24 The physical therapists may have used different patient positioning on the examination table, or their locations for bony landmarks were improper, which might partly explain the low reliability in the hip extension and knee flexion measurements. The results of the PROM measurements are also dependent on the force applied
555
during measurement. The changes in PROM may simply be attributable to day-to-day variations in the force applied to the muscle. We believe that the lower interday reliability of the PROM measurement is not simply because of the repetitive stretching. It has been proposed that ICC values can be accepted as clinically meaningful if the ICC is .80 or greater.42 Although many of the ICC values were .80 or higher in this study, using only the ICC provides an overestimation of the degree of reliability. The fact that lower levels of reliability were measured by the CV than in the ICC can be explained by the fact that these 2 statistical techniques do not measure the same thing. The CV is a more accurate measure of variability. It seems that the CV was not always calculated with the ICC in earlier ROM reliability studies. Interpretation of the results is a major problem when the measured angle is very low, a few degrees below or above zero. This means that total error is also low. Mathematically, this means that reproducibility is good because of the minimal absolute variation. However, with the CV, the opposite is the case. Even a 1° error results in a rather high variation. For example, if the first measurement result is ⫹5° and next measurement is ⫹4°, the error is 20%. Accordingly, although the measurement of the hip flexor tightness is mathematically reproducible, the CV must be considered when estimating the results of therapy. However, although we found high ICC and CV values for both intra- and intertester reliability, significant differences were noted when the mean raw data were compared. Our results may partly be systematically attributable to the effect on the PROM of repetitive stretching. Boone and Azen43 postulated that a 6° difference is acceptable in lower-extremity ROM measurements when more than 1 tester is taking the measurements. Our results are similar, suggesting that a difference of about 5° is statistically significant. By using a constant testing pattern, it is the possibile that the results may be influenced by an ordering effect. The influence of repetition of the testing procedure could have been eliminated by changing the testing order, but this was not done for practical reasons. The PROM measurement should be quick and easy for a physician or a physical therapist to carry out. We did not use separate fixing protocols that would have required a major investment of effort because these can rarely be implemented in clinical practice. However, the measurement protocol was well standardized and blinded so that the physical therapist was not allowed to read the results from the goniometer. A rather wide degree in the variability of the normal ROM of hip has been found among healthy subjects.43-47 In Finland, we do not have population-based normal values for the hip and knee PROM by age and sex. Many of our results are similar to earlier publications, although our testing positions differed. The wide variability of normal ROM values may reflect not only the normal variation but also the error associated with the measurement. It is also possible that muscle stretch ability differs from person to person. CONCLUSIONS Repetitive stretching increased the PROM in hip flexion and inner rotation, but the reproducibility of the PROM measurement did not improve. Results of this study indicate that, for the hip flexion and hip inner rotation, knee goniometric PROM measurements are moderately or highly repeatable in clinical use, but that repeated measurements of hip joints should be primarily taken by the same physical therapist. The reliability of the PROM in hip extension and knee flexion is poor, as assessed in the Thomas test position. Arch Phys Med Rehabil Vol 86, March 2005
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