- Email: [email protected]
Effect of different angles of knee flexion on leg extensor power in healthy individuals
Physiotherapy 98 (2012) 357–360
Technical Report
Effect of different angles of knee flexion on leg extensor power in healthy individuals Karen L. Barker a,b,∗ , Charlotte Crystal a , Meredith Newman a a
b
Physiotherapy Research Unit, Nuffield Orthopaedic Centre NHS Trust, Oxford OX3 7LD, UK The Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, NIHR Biomedical Research Unit, The Nuffield Orthopaedic Centre NHS Trust, Oxford, UK
Abstract Objectives To investigate the effect of fixed flexion knee deformity on leg extensor power as measured by the Nottingham leg extensor power rig. Design Cross-sectional observational study. Setting Orthopaedic hospital. Participants A convenience sample of 135 adult participants. Main outcome measures: leg extensor power normalised for body weight, UCLA activity scale. Results Power values at 0◦ FF were found to be significantly less than power values at 15◦ FF [difference 0.21 W/kg SD .36], and power values at 15◦ FF were significantly less than those at 30◦ FF [difference 0.31 W/kg SD .43; P < 0.001) in both right and left legs. Age and activity levels were moderately negatively correlated, with UCLA score decreasing with increasing age (−0.343, P < 0.0005). No significant correlation was found between activity levels measured on the UCLA and power on the LEP. Conclusions Given the large range of pre-operative maximal extension, the validity of testing each patient at their own maximal range of pre-intervention extension and then at the same angle post-intervention is questionable. In studies assessing change in power following an intervention, the end point angle should be standardised between individuals. In future studies investigating leg extensor power on the LEP rig pre and post intervention, it could be more appropriate to standardise the angle of FF to 30◦ , with individuals who are unable to achieve this position excluded from the study. © 2012 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved. Keywords: Leg extensor power; Knee angle; Fixed flexion deformity
Introduction Many trials of physiotherapy interventions for lower limb pathology have utilised leg extensor power as a primary outcome [1–5]. Leg extensor power (LEP) has been found to be more relevant to mobility and physical functioning than strength alone [6]. It has been shown to be highly correlated with other measures of leg power, such as a single jump [7], timed sit-stand [5,6], stair climbing [8], timed walk [8], and ∗ Corresponding author at: Physiotherapy Research Unit, Nuffield Orthopaedic Centre, Oxford University Hospitals NHS Trust, Windmill Road, Oxford OX3 7HE, UK. Tel.: +44 01865 738080; fax: +44 01865 738043. E-mail address: [email protected] (K.L. Barker).
‘get up and go’ [5]. In elderly people, muscle power is a factor in determining the ease with which a person can stand from a chair or climb stairs and this in turn can significantly affect their health and quality of life. LEP is therefore an important outcome measure being highly functional. The Nottingham LEP rig [9] measures single leg extension power in a seated upright position. It is a reliable and valid measure of LEP [7,10] and between sessions repeatability has been demonstrated in patients with knee osteoarthritis [11]. A significant increase in LEP following knee arthroplasty surgery has been found in both the operated and un-operated legs [1,2,4]. However, the reported assessment protocols have not taken into account the effect of potential changes in knee fixed flexion deformity (FFD) associated with surgery. The presence of FFD has been reported in up to 61% of knees
0031-9406/$ – see front matter © 2012 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.physio.2012.03.001
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K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
undergoing arthroplasty surgery [12]. Fixed flexion deformity affects the biomechanics of the knee joint and may therefore affect maximum LEP, it may also affect the validity of the LEP rig as an outcome measure especially when FFD is expected to change as a result of an intervention such as surgery [13]. The objective of this study was to investigate the effect of fixed flexion knee deformity on LEP as measured by the Nottingham LEP rig in a normal population.
Method Participants A convenience sample of 135 adult participants of varying ages from 16 to 81 with a mean age of 44 years were recruited. Participants were excluded if they had had lower limb or back pain/dysfunction in the last 3 months, previous lower limb surgery, or if they had participated in heavy exercise within the last two hours. All participants were provided with detailed information about the study and gave written informed consent. The study had ethical approval (Ethics Ref. No. 09/H0603/27). Measures All physical measurements were taken by an experienced orthopaedic physiotherapist. Height was recorded in metres (m) using a stadiometer and weight in kilograms (kg) on calibrated scales (with heavy clothing and shoes removed). Range of knee flexion and extension was measured bilaterally using a long armed goniometer (Lafayette Instrument Co., Inc. Model 01135). Each knee position was achieved by moving the LEP seat whilst fully depressing the footplate. The fulcrum of the goniometer was centred over the lateral femoral epicondyle. The proximal arm was aligned with the lateral midline of the femur, using the greater trochanter as a reference point. The distal arm was aligned with the lateral midline of the fibula, using the lateral malleolus as a reference point and once the correct angle was achieved the seat was locked in position Participants were asked to complete the ULCA Activity Scale, a 10 item self-report questionnaire to rate activity level. Leg extensor power (LEP) The Nottingham LEP Rig was used to measure LEP. The procedure for data collection, calibration and calculation has been described in detail previously [7] (Fig. 1). Readings were recorded at three different knee angles for each leg; designed to mimic the flexion contracture deformity present in many patients preoperatively. The angles were (a) full available knee extension (0◦ FF), (b) extension minus 15◦ (15◦ FF), (c) extension minus 30◦ (30◦ FF). The leg and knee angle order were randomised using
Fig. 1. Leg extensor power rig.
computer generated block randomisation and the allocation was concealed using opaque envelopes by an independent assistant. Each knee position was achieved by moving the LEP seat whilst fully depressing the footplate. The knee angle was measured using a long-arm goniometer, aligned with anatomical landmarks and once the correct angle was achieved the seat was locked in position. Participants were instructed to bend their knee and let the footplate come up towards them, then push as hard and as fast as possible after a count of ‘three, two, one push’. At least six measures were taken with at least 15 seconds rest between each attempt. Recordings were stopped once the power values had plateaued. (Maximum values were usually found at 5 to 6 attempts). The recording was repeated for each leg at each of the three knee positions. Data analysis The maximal power reading in watts (W) was recorded; the reading was divided by the participant’s body weight to provide a normalised, more functionally relevant score in W/kg. Data was analysed using the statistical programme SPSS version 19. The data was assessed for normality of distribution at 0◦ , 15◦ and 30◦ FF, using the Kolmogorov–Smirnov test. Results were considered significant at a level of P < 0.05. Comparisons between each knee angle were made using the paired t-test. Measures of association were made using Pearson’s product moment correlation coefficient.
Results The characteristics of the study population are described in Table 1.
K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
359
Table 1 Physical characteristics.
Gender (%) Age (years) Height (in meters) Weight (in kg) BMI ROM right knee flexion ROM left knee flexion ROM right knee extension ROM left knee extension UCLA (1 (lowest) to 10 (highest))
Men Mean (SD) [range]
Women Mean (SD) [range]
63 (47) 45 (18.6); [16 to 80] 1.78 (.07); [1.60 to 1.93] 82 (12); [60 to 119] 26.1 (3.6); [20.6 to 38.1] 133 (9); [115 to 155] 134 (8) [110 to 150] 0 (3); [−10 to +10] 0 (3); [−10 to +10] Median [IQR] 7 [7, 8]
72 (53) 42.6 (16.2)[17 to 76] 1.65 (.07); [1.48 to 1.80] 64 (9); [50 to 87] 23.5 (3.5); [17.9 to 36.3] 134 (8); [110 to 150] 134 (8); [110 to 150] −1 (3); −10 to +5] −1 (3) [−10 to +5] Median [IQR] 8 [7 to 9]
Table 2 Difference in leg extensor power with knee angle. Side
Leg extensor power at 0◦ Mean [SD] (W/kg)
Leg extensor power at 15◦ Mean [SD] (W/kg)
Difference between 0 and 15◦ Mean [SD] (W/kg)
Significance
Leg extensor power at 15◦ Mean [SD] (W/kg)
Leg extensor power at 30◦ Mean [SD] (W/kg)
Difference between 0 and 15◦ Mean [SD] (W/kg)
Significance
Right Left
2.06 [.68] 1.86 [.61]
2.27 [.77] 2.07 [.72]
−.21 [.36] −.21 [.03]
<0.001 <0.001
2.27 [.77] 2.07 [.72]
2.58 [.95] 2.43 [.91]
−.31 [.43] −.36 [.42]
<0.001 <0.001
Power values at 0◦ FF were found to be significantly less than power values at 15◦ FF, and power values at 15◦ FF were significantly less than those at 30◦ FF (P < 0.001) in both right and left legs (Table 2). Age and activity levels were moderately negatively correlated, with UCLA score decreasing with increasing age (−0.343, P < 0.0005). No significant correlation was found between activity levels measured on the UCLA and power on the LEP.
Discussion Significantly higher LEP values were found with increasing knee flexion starting positions. This was achieved by bringing the seat closer to the footplate, providing an artificial constraint and simulating a FFD. Bassey et al. [14] showed that increasing start angles of knee flexion (also by bringing the seat position closer to the footplate) produced higher values of LEP with the optimal start angle being 82.5◦ flexion. This was thought to be due to the mechanical advantages of the hip, knee and ankle in these positions. This study was devised to replicate the normal clinical presentation, where most patients who are undergoing knee arthroplasty present with some fixed flexion knee deformity [13]. Our evidence shows that the greater the degree of FF, the greater the mechanical advantage the patient may have in terms of producing explosive power on the LEP rig. Traditionally, in assessing LEP pre- and post-intervention where the degree of fixed flexion is likely to change, the seat
position for each patient is standardised to the preintervention distance that the individual is able to achieve at maximal knee extension, so that individual’s power can be compared accurately pre- and post-intervention. In published studies of cohorts of patients undergoing knee arthroplasty pre-operative range of maximal knee extension has been reported to be up to 50◦ FFD [15,16]. In a study of 5562 knees Ritter et al. reported that 8.5% had between 20 and 50◦ of flexion contracture and 26.5% had flexion contracture of between 6 and 19◦ [16]. Given the large range of pre-operative maximal extension, the validity of testing each patient at their own maximal range of pre-intervention extension and then at the same angle post-intervention is questionable, as those with greater FFD pre-intervention may have a greater mechanical advantage in terms of producing explosive power, compared with those with a smaller angle of FFD. Therefore, in studies assessing change in power following an intervention, it could be argued that the actual end point angle should be standardised between individuals. In future studies investigating leg extensor power on the LEP rig pre- and post-intervention, it could be more appropriate to standardise the angle of FF to 30◦ , with individuals who are unable to achieve this position excluded from the study. Ethical approval: The study had ethical approval from Oxfordshire Research Ethics Committee (Ethics Ref No.: 09/H0603/27). Funding: The study was funded by an Internal Department Bursary. Conflict of interest: None declared.
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K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
References [1] Lamb S, Frost H. Recovery of mobility after knee athroplasty: expected rates and influencing factors. J Arthroplasty 2003;18(5):575–82. [2] Minns Lowe C, Barker KL, Holder R, Sackley CM. Comparison of post-discharge physiotherapy versus usual care following primary total knee arthroplasty for osteoarthritis: an exploratory pilot randomized clinical trial. Clin Rehabil 2011 [epub ahead of print December 16]. [3] Braid V, Barber M, Mitchell S, Martin B, Granat M, Scott D. Randomised controlled trial of electrical stimulation of the quadriceps after proximal femoral fracture. Aging Clin Exp Res 2008;20(1):62–6. [4] Barker K, Jenkins C, Pandit H, Murray D. Muscle power and function two years after unicompartmental knee replacement. Knee 2011;(June 9) [Epub ahead of print]. [5] Capodaglio P, Capadaglio EM, Facioli M, Saibene F. Long term strength training for community dwelling people over 75: impact on muscle function, functional activity and life style. Eur J Appl Physiol 2007;100:535–42. [6] Skelton D, Greig C, Davies J, Young A. Strength, power and related functional ability of healthy people aged 65–89 years. Age Ageing 1994;23(5):371–7. [7] Bassey E, Short A. A new method for measuring power output in a single leg extension: feasibility, reliability and validity. Eur J Appl Physiol 1990;60:385–90.
[8] Bassey E, Fiatarone M, O’Neill E, Kelly M, Evans W, Lipsitz L. Leg extensor power and functional performance in very old men and women. Clin Sci 1992;82:321–7. [9] University of Nottingham, Medical Engineering Unit. Available from: http://www.nottingham.ac.uk/shared/shared meu/components/leg rig.pdf. [10] Blackwell T, Cawthorn PM, Marshall LM, Brand R. Consistency of leg extensor power assessments in older men: the osteoporotic fractures in men (MrOS) study. Arch Phys Med Rehabil 2009;88:934–40. [11] Robertson S, Frost H, Doll H, O’Connor J. Leg extensor power and quadriceps strength: an assessment of repeatability in patients with osteoarthritic knees. Clin Rehabil 1998;12:120–6. [12] Tew M, Forster I. Effect of knee replacement on flexion deformity. J Bone Joint Surg (Br) 1987;69B(3):395–9. [13] Aderinto J, Brenkel I, Chan P. Natural history of fixed flexion deformity following total knee replacement; a prospective five-year study. J Bone Joint Surg (Br) 2005;87(7):934–6. [14] Bassey E, Delbridge A, Short A. The effect of limb joint angles on the extensor power output of the leg in man. J Physiol 1989;420(51P). [15] Cheng K, Ridley D, Bird J, McLeod G. Patients with fixed flexion deformity after total knee arthroplasty do just as well as those without: ten year prospective data. Int Orthop 2010;34(5):663–9. [16] Ritter MA, Lutring JD, Davis KE, Berend ME, Person JL, Meneghini RM. The role of flexion contracture on outcomes in primary total knee arthroplasty. J Arthroplasty 2007;22:1092–6.
Available online at www.sciencedirect.com
Technical Report
Effect of different angles of knee flexion on leg extensor power in healthy individuals Karen L. Barker a,b,∗ , Charlotte Crystal a , Meredith Newman a a
b
Physiotherapy Research Unit, Nuffield Orthopaedic Centre NHS Trust, Oxford OX3 7LD, UK The Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, NIHR Biomedical Research Unit, The Nuffield Orthopaedic Centre NHS Trust, Oxford, UK
Abstract Objectives To investigate the effect of fixed flexion knee deformity on leg extensor power as measured by the Nottingham leg extensor power rig. Design Cross-sectional observational study. Setting Orthopaedic hospital. Participants A convenience sample of 135 adult participants. Main outcome measures: leg extensor power normalised for body weight, UCLA activity scale. Results Power values at 0◦ FF were found to be significantly less than power values at 15◦ FF [difference 0.21 W/kg SD .36], and power values at 15◦ FF were significantly less than those at 30◦ FF [difference 0.31 W/kg SD .43; P < 0.001) in both right and left legs. Age and activity levels were moderately negatively correlated, with UCLA score decreasing with increasing age (−0.343, P < 0.0005). No significant correlation was found between activity levels measured on the UCLA and power on the LEP. Conclusions Given the large range of pre-operative maximal extension, the validity of testing each patient at their own maximal range of pre-intervention extension and then at the same angle post-intervention is questionable. In studies assessing change in power following an intervention, the end point angle should be standardised between individuals. In future studies investigating leg extensor power on the LEP rig pre and post intervention, it could be more appropriate to standardise the angle of FF to 30◦ , with individuals who are unable to achieve this position excluded from the study. © 2012 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved. Keywords: Leg extensor power; Knee angle; Fixed flexion deformity
Introduction Many trials of physiotherapy interventions for lower limb pathology have utilised leg extensor power as a primary outcome [1–5]. Leg extensor power (LEP) has been found to be more relevant to mobility and physical functioning than strength alone [6]. It has been shown to be highly correlated with other measures of leg power, such as a single jump [7], timed sit-stand [5,6], stair climbing [8], timed walk [8], and ∗ Corresponding author at: Physiotherapy Research Unit, Nuffield Orthopaedic Centre, Oxford University Hospitals NHS Trust, Windmill Road, Oxford OX3 7HE, UK. Tel.: +44 01865 738080; fax: +44 01865 738043. E-mail address: [email protected] (K.L. Barker).
‘get up and go’ [5]. In elderly people, muscle power is a factor in determining the ease with which a person can stand from a chair or climb stairs and this in turn can significantly affect their health and quality of life. LEP is therefore an important outcome measure being highly functional. The Nottingham LEP rig [9] measures single leg extension power in a seated upright position. It is a reliable and valid measure of LEP [7,10] and between sessions repeatability has been demonstrated in patients with knee osteoarthritis [11]. A significant increase in LEP following knee arthroplasty surgery has been found in both the operated and un-operated legs [1,2,4]. However, the reported assessment protocols have not taken into account the effect of potential changes in knee fixed flexion deformity (FFD) associated with surgery. The presence of FFD has been reported in up to 61% of knees
0031-9406/$ – see front matter © 2012 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.physio.2012.03.001
358
K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
undergoing arthroplasty surgery [12]. Fixed flexion deformity affects the biomechanics of the knee joint and may therefore affect maximum LEP, it may also affect the validity of the LEP rig as an outcome measure especially when FFD is expected to change as a result of an intervention such as surgery [13]. The objective of this study was to investigate the effect of fixed flexion knee deformity on LEP as measured by the Nottingham LEP rig in a normal population.
Method Participants A convenience sample of 135 adult participants of varying ages from 16 to 81 with a mean age of 44 years were recruited. Participants were excluded if they had had lower limb or back pain/dysfunction in the last 3 months, previous lower limb surgery, or if they had participated in heavy exercise within the last two hours. All participants were provided with detailed information about the study and gave written informed consent. The study had ethical approval (Ethics Ref. No. 09/H0603/27). Measures All physical measurements were taken by an experienced orthopaedic physiotherapist. Height was recorded in metres (m) using a stadiometer and weight in kilograms (kg) on calibrated scales (with heavy clothing and shoes removed). Range of knee flexion and extension was measured bilaterally using a long armed goniometer (Lafayette Instrument Co., Inc. Model 01135). Each knee position was achieved by moving the LEP seat whilst fully depressing the footplate. The fulcrum of the goniometer was centred over the lateral femoral epicondyle. The proximal arm was aligned with the lateral midline of the femur, using the greater trochanter as a reference point. The distal arm was aligned with the lateral midline of the fibula, using the lateral malleolus as a reference point and once the correct angle was achieved the seat was locked in position Participants were asked to complete the ULCA Activity Scale, a 10 item self-report questionnaire to rate activity level. Leg extensor power (LEP) The Nottingham LEP Rig was used to measure LEP. The procedure for data collection, calibration and calculation has been described in detail previously [7] (Fig. 1). Readings were recorded at three different knee angles for each leg; designed to mimic the flexion contracture deformity present in many patients preoperatively. The angles were (a) full available knee extension (0◦ FF), (b) extension minus 15◦ (15◦ FF), (c) extension minus 30◦ (30◦ FF). The leg and knee angle order were randomised using
Fig. 1. Leg extensor power rig.
computer generated block randomisation and the allocation was concealed using opaque envelopes by an independent assistant. Each knee position was achieved by moving the LEP seat whilst fully depressing the footplate. The knee angle was measured using a long-arm goniometer, aligned with anatomical landmarks and once the correct angle was achieved the seat was locked in position. Participants were instructed to bend their knee and let the footplate come up towards them, then push as hard and as fast as possible after a count of ‘three, two, one push’. At least six measures were taken with at least 15 seconds rest between each attempt. Recordings were stopped once the power values had plateaued. (Maximum values were usually found at 5 to 6 attempts). The recording was repeated for each leg at each of the three knee positions. Data analysis The maximal power reading in watts (W) was recorded; the reading was divided by the participant’s body weight to provide a normalised, more functionally relevant score in W/kg. Data was analysed using the statistical programme SPSS version 19. The data was assessed for normality of distribution at 0◦ , 15◦ and 30◦ FF, using the Kolmogorov–Smirnov test. Results were considered significant at a level of P < 0.05. Comparisons between each knee angle were made using the paired t-test. Measures of association were made using Pearson’s product moment correlation coefficient.
Results The characteristics of the study population are described in Table 1.
K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
359
Table 1 Physical characteristics.
Gender (%) Age (years) Height (in meters) Weight (in kg) BMI ROM right knee flexion ROM left knee flexion ROM right knee extension ROM left knee extension UCLA (1 (lowest) to 10 (highest))
Men Mean (SD) [range]
Women Mean (SD) [range]
63 (47) 45 (18.6); [16 to 80] 1.78 (.07); [1.60 to 1.93] 82 (12); [60 to 119] 26.1 (3.6); [20.6 to 38.1] 133 (9); [115 to 155] 134 (8) [110 to 150] 0 (3); [−10 to +10] 0 (3); [−10 to +10] Median [IQR] 7 [7, 8]
72 (53) 42.6 (16.2)[17 to 76] 1.65 (.07); [1.48 to 1.80] 64 (9); [50 to 87] 23.5 (3.5); [17.9 to 36.3] 134 (8); [110 to 150] 134 (8); [110 to 150] −1 (3); −10 to +5] −1 (3) [−10 to +5] Median [IQR] 8 [7 to 9]
Table 2 Difference in leg extensor power with knee angle. Side
Leg extensor power at 0◦ Mean [SD] (W/kg)
Leg extensor power at 15◦ Mean [SD] (W/kg)
Difference between 0 and 15◦ Mean [SD] (W/kg)
Significance
Leg extensor power at 15◦ Mean [SD] (W/kg)
Leg extensor power at 30◦ Mean [SD] (W/kg)
Difference between 0 and 15◦ Mean [SD] (W/kg)
Significance
Right Left
2.06 [.68] 1.86 [.61]
2.27 [.77] 2.07 [.72]
−.21 [.36] −.21 [.03]
<0.001 <0.001
2.27 [.77] 2.07 [.72]
2.58 [.95] 2.43 [.91]
−.31 [.43] −.36 [.42]
<0.001 <0.001
Power values at 0◦ FF were found to be significantly less than power values at 15◦ FF, and power values at 15◦ FF were significantly less than those at 30◦ FF (P < 0.001) in both right and left legs (Table 2). Age and activity levels were moderately negatively correlated, with UCLA score decreasing with increasing age (−0.343, P < 0.0005). No significant correlation was found between activity levels measured on the UCLA and power on the LEP.
Discussion Significantly higher LEP values were found with increasing knee flexion starting positions. This was achieved by bringing the seat closer to the footplate, providing an artificial constraint and simulating a FFD. Bassey et al. [14] showed that increasing start angles of knee flexion (also by bringing the seat position closer to the footplate) produced higher values of LEP with the optimal start angle being 82.5◦ flexion. This was thought to be due to the mechanical advantages of the hip, knee and ankle in these positions. This study was devised to replicate the normal clinical presentation, where most patients who are undergoing knee arthroplasty present with some fixed flexion knee deformity [13]. Our evidence shows that the greater the degree of FF, the greater the mechanical advantage the patient may have in terms of producing explosive power on the LEP rig. Traditionally, in assessing LEP pre- and post-intervention where the degree of fixed flexion is likely to change, the seat
position for each patient is standardised to the preintervention distance that the individual is able to achieve at maximal knee extension, so that individual’s power can be compared accurately pre- and post-intervention. In published studies of cohorts of patients undergoing knee arthroplasty pre-operative range of maximal knee extension has been reported to be up to 50◦ FFD [15,16]. In a study of 5562 knees Ritter et al. reported that 8.5% had between 20 and 50◦ of flexion contracture and 26.5% had flexion contracture of between 6 and 19◦ [16]. Given the large range of pre-operative maximal extension, the validity of testing each patient at their own maximal range of pre-intervention extension and then at the same angle post-intervention is questionable, as those with greater FFD pre-intervention may have a greater mechanical advantage in terms of producing explosive power, compared with those with a smaller angle of FFD. Therefore, in studies assessing change in power following an intervention, it could be argued that the actual end point angle should be standardised between individuals. In future studies investigating leg extensor power on the LEP rig pre- and post-intervention, it could be more appropriate to standardise the angle of FF to 30◦ , with individuals who are unable to achieve this position excluded from the study. Ethical approval: The study had ethical approval from Oxfordshire Research Ethics Committee (Ethics Ref No.: 09/H0603/27). Funding: The study was funded by an Internal Department Bursary. Conflict of interest: None declared.
360
K.L. Barker et al. / Physiotherapy 98 (2012) 357–360
References [1] Lamb S, Frost H. Recovery of mobility after knee athroplasty: expected rates and influencing factors. J Arthroplasty 2003;18(5):575–82. [2] Minns Lowe C, Barker KL, Holder R, Sackley CM. Comparison of post-discharge physiotherapy versus usual care following primary total knee arthroplasty for osteoarthritis: an exploratory pilot randomized clinical trial. Clin Rehabil 2011 [epub ahead of print December 16]. [3] Braid V, Barber M, Mitchell S, Martin B, Granat M, Scott D. Randomised controlled trial of electrical stimulation of the quadriceps after proximal femoral fracture. Aging Clin Exp Res 2008;20(1):62–6. [4] Barker K, Jenkins C, Pandit H, Murray D. Muscle power and function two years after unicompartmental knee replacement. Knee 2011;(June 9) [Epub ahead of print]. [5] Capodaglio P, Capadaglio EM, Facioli M, Saibene F. Long term strength training for community dwelling people over 75: impact on muscle function, functional activity and life style. Eur J Appl Physiol 2007;100:535–42. [6] Skelton D, Greig C, Davies J, Young A. Strength, power and related functional ability of healthy people aged 65–89 years. Age Ageing 1994;23(5):371–7. [7] Bassey E, Short A. A new method for measuring power output in a single leg extension: feasibility, reliability and validity. Eur J Appl Physiol 1990;60:385–90.
[8] Bassey E, Fiatarone M, O’Neill E, Kelly M, Evans W, Lipsitz L. Leg extensor power and functional performance in very old men and women. Clin Sci 1992;82:321–7. [9] University of Nottingham, Medical Engineering Unit. Available from: http://www.nottingham.ac.uk/shared/shared meu/components/leg rig.pdf. [10] Blackwell T, Cawthorn PM, Marshall LM, Brand R. Consistency of leg extensor power assessments in older men: the osteoporotic fractures in men (MrOS) study. Arch Phys Med Rehabil 2009;88:934–40. [11] Robertson S, Frost H, Doll H, O’Connor J. Leg extensor power and quadriceps strength: an assessment of repeatability in patients with osteoarthritic knees. Clin Rehabil 1998;12:120–6. [12] Tew M, Forster I. Effect of knee replacement on flexion deformity. J Bone Joint Surg (Br) 1987;69B(3):395–9. [13] Aderinto J, Brenkel I, Chan P. Natural history of fixed flexion deformity following total knee replacement; a prospective five-year study. J Bone Joint Surg (Br) 2005;87(7):934–6. [14] Bassey E, Delbridge A, Short A. The effect of limb joint angles on the extensor power output of the leg in man. J Physiol 1989;420(51P). [15] Cheng K, Ridley D, Bird J, McLeod G. Patients with fixed flexion deformity after total knee arthroplasty do just as well as those without: ten year prospective data. Int Orthop 2010;34(5):663–9. [16] Ritter MA, Lutring JD, Davis KE, Berend ME, Person JL, Meneghini RM. The role of flexion contracture on outcomes in primary total knee arthroplasty. J Arthroplasty 2007;22:1092–6.
Available online at www.sciencedirect.com