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The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients
Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
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Original Research
The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients+ Evgeni Rozenfeld a, b, *, Aharon S. Finestone c, Uria Moran a, Elad Damri a, b, Leonid Kalichman b a
Israel Defense Force, Medical Corps, Israel Department of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel c Assaf HaRofeh Medical Center, Zeriffin, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 May 2019 Accepted 9 May 2019
Background: Anterior knee pain (AKP) is a widespread problem among young athletes and soldiers. There are many theories on the etiology of AKP but there is little reference to myofascial trigger points (MTrPs) as a possible contributor. Aim: To evaluate the association between AKP and prevalence of active and latent MTrPs in the hip and thigh muscles in soldiers. Methods: A cross-sectional study was conducted in the Beer-Sheva military outpatient physical therapy clinic. Subjects were 42 men and 23 women referred for physical therapy, 33 with a diagnosis of AKP (cases) and 32 with upper limb complaints (without AKP, controls). All subjects underwent physical evaluation by an examiner blinded to their identity and medical condition. The following muscles were assessed bilaterally for active or latent MTrPs: rectus femoris (proximal), vastus medialis (middle and distal), vastus lateralis (middle and distal) and gluteus medius (anterior, posterior and distal). Results: In six out of eight areas, the cases had a higher prevalence of total active and latent MTrPs than the controls. When summarizing MTrPs by muscle, cases had significantly more MTrPs than controls in each muscle. The largest difference was found in vastus medialis and vastus lateralis; nearly half of the cases had MTrPs in these muscles. Conclusions: Subjects with AKP have a greater prevalence of MTrPs in their hip and thigh muscles than controls, indicating an association between MTrPs and AKP. Further research is necessary to determine whether MTrPs are the cause or the consequence of AKP. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Myofascial trigger points Anterior knee pain Prevalence
1. Introduction The knee is one of the most common sites of injury in athletes and recruits and patellofemoral or anterior knee pain (AKP) constitutes nearly 25% of injuries to the knee (Taunton and Ryan, 2002). AKP is found in high prevalence among military personnel. Studies have found that 12e15% of army recruits worldwide complained of AKP(Boling et al., 2010; Milgrom et al., 1991). Many theories have
+ Results of this study were presented during 8th Conference of International Academy of Manual Musculoskeletal Medicine, Padua, Italy, November 2016. * Corresponding author. Department of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel. E-mail address: [email protected] (E. Rozenfeld).
been proposed to explain the etiology of AKP, including excessive mechanical loading and chemical irritation of local nerve endings (Dye, 1996; LaBella, 2004), malalignment of the patella relative to the femoral trochlea, ischemia in the lateral retinaculum, overuse, and muscular imbalance (Sanchis-Alfonso, 2008). In general, the literature suggests multifactorial etiology of AKP (Hiemstra et al., 2014). None of these theories include a myofascial origin for AKP. Nevertheless, several studies indicate that Myofascial trigger points (MTrPs) can be associated with other knee problems (Alburquerque-García et al., 2015; Torres-Chica et al., 2014). Myofascial pain syndrome is a common form of somatic pain arising from muscles (Borg-Stein and Simons, 2002). MTrPs are the main component of this syndrome (Chang-Zern Hong, 2006; Gerwin, 2010; Simons et al., 1999), defined as a hyperirritable spots within a palpable taut band of a skeletal muscle that is painful on
https://doi.org/10.1016/j.jbmt.2019.05.010 1360-8592/© 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
List of abbreviations BMI GM MTrP QF RF VL VM
body mass index gluteus medius myofascial trigger point quadratus femoris rectus femoris vastus lateralis vastus medialis
compression, stretch, or overload, and that gives rise to a referred pain (Simons et al., 1999). The diagnosis of MTrPs is a clinical skill based on palpation, following the diagnostic criteria established by Simons et al. (1999) and Gerwin et al. (1997). Published studies have reported poor to good reliability for MTrPs palpation (Al-Shenqiti and Oldham, 2005; Bron et al., 2007; Gerwin et al., 1997; Hsieh et al., 2000; Nice et al., 1992; Njoo and Van Der Does, 1994; Zuil-Escobar et al., 2016). Lately, Rozenfeld et al. (2017) found that MTrP palpation is a moderately reliable diagnostic tool in the hip and thigh muscles and it can be used in clinical practice and research. Another recent study by Walsh et al. (2017)suggests that palpation is a reliable method for locating MTrPs in the VM and VL. Numerous studies on the upper limb muscles have shown a significantly greater number of active MTrPs on the painful side (Alburquerque-Sendín et al., 2013; Bron et al., 2011; Ge et al., 2008). However, very few studies have explored the association between MTrPs and pain in the lower limb, and only two looked for MTrPs in hip and thigh muscles in patients with AKP (Dippenaar et al., 2008; Smith, 2012). A recently published review suggested that there is initial evidence to the assumption that MTrPs may play a role in pain and disability of patients with knee osteoarthritis (Dor and Kalichman, 2017). The aims of this study were: To evaluate the association between AKP and prevalence of active and latent MTrPs in hip and thigh muscles in soldiers. To evaluate the association between the number of MTrPs and severity of AKP complaints. Hypotheses: MTrPs are more prevalent in the hip and thigh muscles in soldiers complaining of AKP, than in those without AKP. In subjects with AKP, the number of MTrPs is associated with the more severe condition (as reflected by the Western Ontario and McMaster Universities Arthritis Index (WOMAC).
their study of MTrPs in the hip in AKP patients and by other casecontrol studies on the prevalence of myofascial pain (Carnero et al., 2008). Inclusion criteria for the case group were: Age between 18 and 30 and referral for physical therapy by a physician due to AKP present for >6 weeks. (i.e. retropatellar pain which increased in weight-bearing activities such as jumping, running, squatting, and going up or down stairs or in prolonged sitting with flexed knees), and a positive patellar grinding test. Exclusion criteria were: Any severe medical condition that may be a contraindication for physical treatment; participation in another interventional clinical trial; history of major trauma or operation in lower limb; positive findings in the examination of knee ligaments; menisci; bursa; iliotibial band; patellar tendons and their insertions; knee pain originating from osteoarthritis; history of major psychiatric or neurological illness; fibromyalgia or other systemic rheumatic diseases; pregnancy. None of the subjects had met the examiner before the study. Ethics: All subjects received an explanation about the study and signed an informed consent form. The study was approved by the Israel Defense Forces ethical review board (Approval No. 1427e2014). Evaluation procedure: Each subject completed the demographic questionnaire and WOMAC. In subjects with bilateral pain, the questionnaires referred to the more painful knee. They had a complete orthopedic evaluation, followed by an examination of 4 muscles of each leg for MTrPs. The examiner that performed the MTrP evaluation was a physical therapist with at least 6 years of practice including myofascial evaluation and treatment. The examiner was blinded to subjects' identities and medical condition. Demographic data on age, sex, occupation, leisure physical activity, health history, data on present disease (onset of symptoms, previous treatments etc.), weight and height were collected. WOMAC questionnaire: Each participant was asked to fill the Hebrew version of the WOMAC questionnaire. WOMAC is a disease-specific, purpose-built, high-performance instrument for evaluating pain, joint stiffness, and function in knee and hip osteoarthritis clinical trials. It has been extensively validated and is recommended by the Osteoarthritis Research Society. The WOMAC questionnaire has a visual analog scale ranging from 0 to 10 cm, where 0 cm indicates no pain or limitation in function and 10 cm indicates the most severe pain or limitation in function. It has 3 subscales: pain (5 items) stiffness (2 items) and function (17 items). All the subscales have high test-retest reliability, and validation studies have shown high correlations with other indices probing the same dimensions (B, 2015; Bellamy et al., 1988; McConnell et al., 2001). Furthermore, the Hebrew version of WOMAC was found to be reliable and valid for use in Israeli patients with knee OA (Wigler et al., 1999). Reliability: intra-class coefficients ranged from 0.12 to 0.69 (p < 0.01). MTrP assessment: The examiners performed an evaluation of MTrPs using a flat palpation technique, according to the diagnostic criteria established by Simons et al. (1999) to identify the following:
2. Methods Design: Observational, exploratory, cross-sectional study. Prevalence of MTrPs was evaluated in patients with AKP and matched controls without knee pain. Setting: Physical Therapy Department, Military outpatient clinic, Beer Sheva, Israel. Subjects: We recruited 65 soldiers and officers (42 men and 23 women) who were referred for physical therapy due to various medical conditions. Cases (N ¼ 33) had been referred for physical therapy with a diagnosis of AKP and controls (N ¼ 32) had been referred with upper limb complaints and had no complaints about knee pain. A similar sample size was used by Roach et al. (2013) in
The presence of a taut band. The presence of a tender spot on the taut band during palpation. Reproduction of referred pain during MTrP compression. All criteria were scored dichotomously, as presence or absence of each criterion. If the examiner was unsure of the result, he was instructed to score that specific criterion as absent. All subjects were asked if the palpation caused referred pain and if the referred pain was relevant to their complaint. Prior to the blinded examination, controls (without knee pain) had been instructed to answer the question on the relevance of the referred pain negatively. Definition of the active and latent MTrPs was made by
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
summation of the diagnostic criteria. A point was considered as MTrP when a taut band, tenderness, and referred pain were all present. If the subject answered that the referred pain was relevant to their complaints the MTrP was labeled as active. If not, the MTrP was considered latent. The evaluation was performed in 8 areas of four muscles in both legs. Vastus lateralis (VL): middle and distal, vastus medialis (VM): middle and distal, gluteus medius (GM): anterior, posterior and distal, and rectus femoris (RF). These muscles were chosen as MTrPs in these areas refer pain to the anterior knee region (Travell and Simons, 1992) and can potentially cause AKP due to muscle weakness and imbalance (Barton et al., 2013; Meira and Brumitt, 2011; Prins and van der Wurff, 2009). There are more muscles that refer to the knee, yet based on the researchers’ clinical experience, only those areas were included. The intra- and inter-rater reliability of the aforementioned MTrP detection has been evaluated and reported (Rozenfeld et al., 2017). 2.1. Statistical analysis All statistical analysis was performed using the SPSS statistical package (Version 17). Significance levels were set at p < 0.05. Descriptive statistics were used to characterize the study sample. We used independent T-test and c2 test to compare demographic characteristics and WOMAC results between cases and controls. To compare the prevalence of MTrPs between subjects with and without AKP a c2 test was used. The measuring scale was nominal. Since significant differences were not found in the prevalence of MTrPs between both legs in the control group (McNemar's test was p > 0.05 between left and right legs in all cases), it was decided to compare MTrPs prevalence in the right leg of controls, to the affected leg of cases (the more painful leg was used in subjects with AKP). To evaluate the association between MTrPs prevalence and WOMAC, Spearman's correlation was used. A special MTrP score summarizing the MTrP prevalence in all areas of each subject was created. The score ranged from 0 to 8 (0 means that there are no MTrPs in any of the areas that were evaluated, whereas 8 means that there was an MTrP in each of those areas). Since an active MTrP is composed of latent MTrPs together with “referred pain relevant to patient complaints”, to avoid double scoring it was determined that if an active MTrP was positive, then the latent MTrP would be marked as negative. This way, only one of the points can be positive at a given time. Data on two types of MTrPs are presented in the results: active and latent. The total MTrPs were also calculated (the summation of active and latent MTrPs) and presented. 3. Results Study participants’ characteristics are summarized in Table 1. In total 65 subjects (18 males and 15 females in the case group and 24
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males and 8 females in the control group) met the inclusion criteria and agreed to participate in this study. There was no significant difference between the groups in any of the demographic parameters (age, BMI, service period, sex, and type of military service). Table 2 presents the comparison between the MTrP prevalence in the right leg of the controls to the affected leg of the cases in all studied areas. Data are presented according to the prevalence of MTrP in each of eight muscle areas. For each area, data on three types of MTrP are presented (active, latent and total MTrP). In six out of eight areas, cases had a higher prevalence of total MTrPs than controls. The difference was significant for all areas except anterolateral and posterior GM. The strongest difference was in mid VM and distal VL (11, 33.3%, total MTrPs in cases vs. 0 in controls; c2 ¼ 12.840, d.f. ¼ 1, p ¼ 0.0001). A logic summation of MTrPs by muscles was performed, which is to say that if one of the areas in the muscle had a MTrP, then the muscle was considered positive for MTrPs. For example, if middle VMO had an active MTrP, whereas distal VM did not, VM was marked as positive for active MTrP. As shown in Table 3, cases had
Table 2 Comparison of MTrP prevalence between right leg in the control group (N ¼ 32) and the affected leg in case group (N ¼ 33). MTrPs
Right
Affected
Rt vs. Affected**
Latent MTrP RF Active MTrP RF Total MTrP RF
0 0 0
1 (3.0%) 5 (15.2%) 6 (18.2%)
c2 ¼ 0.985, p ¼ 1.00 c2 ¼ 5.253, p ¼ 0.05 c2¼6.410, p¼0.02
Latent MTrP Middle VM Active MTrP Middle VM Total MTrP Middle VM
0 0 0
0 11 (33.3%) 11 (33.3%)
c2¼12.840, p¼0.0001 c2¼12.840, p¼0.0001
Latent MTrP Distal VM Active MTrP Distal VM Total MTrP Distal VM
1 (3.1%) 0 1 (3.1%)
0 11 (33.3%) 11 (33.3%)
c2 ¼ 1.047, p ¼ 0.49 c2¼12.840, p¼0.0001 c2¼9.849, p¼0.002
Latent MTrP Middle VL Active MTrP Middle VL Total MTrP Middle VL
0 0 0
2 (6.1%) 8 (24.2%) 10 (30.3%)
c2 ¼ 2.001, p ¼ 0.49 c2¼8.846, p¼0.005 c2¼11.460, p¼0.001
Latent MTrP Distal VL Active MTrP Distal VL Total MTrP Distal VL
0 0 0
0 11 (33.3%) 11 (33.3%)
c2¼12.840, p¼0.0001 c2¼12.840, p¼0.0001
Latent MTrP Anterolateral GM Active MTrP Anterolateral GM Total MTrP Anterolateral GM
0 0 0
2 (6.1%) 0 2 (6.1%)
c2 ¼ 2.001, p ¼ 0.49
Latent MTrP Posterior GM Active MTrP Posterior GM Total MTrP Posterior GM
2 (6.3%) 0 2 (6.3%)
2 (6.1%) 6 (18.2%) 8 (24.2%)
c2 ¼ 0.001, p ¼ 1.00 c2¼6.410, p¼0.024 c2 ¼ 4.040, p ¼ 0.08
Latent MTrP Distal GM Active MTrP Distal GM Total MTrP Distal GM
0 0 0
3 (9.1%) 6 (18.2%) 9 (27.3%)
c2 ¼ 3.050, p ¼ 0.23 c2¼6.410, p¼0.024 c2¼10.130, p¼0.002
c2 ¼ 2.001, p ¼ 0.49
a Results of chi-square test; RT-right, LT-left; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; RF-rectus femoris, VM-vastus medialis, VL-vastus lateralis, GM-gluteus medius; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
Table 1 Descriptive statistics of cases and controls. Characteristics
Case group (N ¼ 33)
Control group (N ¼ 32)
Comparison*
Age (years) BMI (kg/m2) Service period (months)
20.49 ± 2.00 23.60 ± 3.35 16.39 ± 15.6
20.98 ± 2.11 23.35 ± 4.17 22.13 ± 13.91
T ¼ 0.960, p ¼ 0.34 T ¼ 0.268, p ¼ 0.78 T ¼ 1.561, p ¼ 0.12
Sex (Males) Type of service
18 (54.5%) 10 (30.3%) 14 (42.4%) 9 (27.3%)
24 (75%) 12 (37.5%) 6 (18.8%) 14 (43.8%)
c2 ¼ 2.973, d.f. ¼ 1, p ¼ 0.07 c2 ¼ 4.454, d.f. ¼ 2, p ¼ 0.10
Comparison**
a
Results of Independent T-Test;
Combat Support Office b
Results of chi-square test; BMI-body mass index.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
Table 3 Comparison of MTrP by muscles, control Rt. Vs. cases affected. Muscle
Right limb controls (N ¼ 32)
Affected limb cases (N ¼ 33)
Comparison Right vs. affected*
RF
Latent MTrP Active MTrP Total MTrP
0 0 0
1 (3.0%) 5 (15.2%) 6 (18.2%)
c2 ¼ 0.985, p ¼ 1.00 c2 ¼ 5.253, p ¼ 0.05 c2¼6.410, p¼0.024
VM
Latent MTrP Active MTrP Total MTrP
1 (3.1%) 0 1 (3.1%)
0 15 (45.5%) 15 (45.5%)
c2 ¼ 1.047, p ¼ 0.49 c2¼18.909, p¼0.0001 c2¼15.687, p¼0.0001
VL
Latent MTrP Active MTrP Total MTrP
0 0 0
2 (6.1%) 16 (48.5%) 16 (48.5%)
c2 ¼ 2.001, p ¼ 0.49 c2¼20.587, p¼0.0001 c2¼20.587, p¼0.0001
GM
Latent MTrP Active MTrP Total MTrP
2 (6.3%) 0 2 (6.3%)
5 (15.2%) 7 (21.2%) 12 (36.4%)
c2 ¼ 1.340, p ¼ 0.42 c2¼7.607, p¼0.01 c2¼8.718, p¼0.003
a Results of chi-square test; RF-rectus femoris, VM-vastus medialis, VL-vastus lateralis, GM-gluteus medius; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
significantly more total MTrPs than controls in all evaluated muscles. The largest prevalence of total MTrPs was found in VL muscle; 16 (48.5%) total MTrPs in the case group, whereas in the control group there were 0 total MTrPs (c2 ¼ 20.587, d.f. ¼ 1, p ¼ 0.0001). The smallest, yet significant difference was in RF muscle with 6 (18.2%) total MTrPs in cases and 0 total MTrPs in controls (c2 ¼ 6.410, d.f. ¼ 1, p ¼ 0.024). When summarizing MTrPs in the entire limb (if one of the evaluated areas had a positive MTrP, then the whole limb was considered positive for MTrPs) (Table 4), 78.8% of the subjects in the case group had at least one MTrP in the evaluated limb whereas only 6.3% of the subjects in the control group had any MTrP in the evaluated limb (c2 ¼ 34.862, d.f. ¼ 1, p ¼ 0.0001). Table 5 presents the Spearman's correlations between the MTrP score and WOMAC, results while Fig. 1 shows a scatterplot of WOMAC disability subscale versus the total MTrPs. The sum of all latent MTrPs and all active MTrPs showed no correlation to any of the WOMAC subscales. The total MTrPs showed a significant positive correlation to WOMAC disability (r ¼ 0.36, p ¼ 0.04) and there was no correlation to any other score. 4. Discussion Only a few previous studies suggested MTrPs as a potential cause of AKP (Roach et al., 2013; Smith, 2012). This is the first extensive report on the prevalence of MTrPs in hip and thigh muscles in patients with AKP. This study demonstrates a significant difference between cases and controls in the prevalence of MTrPs in most studied areas (Fig. 2). When we compared the affected leg in cases to the right leg in controls we found that cases had a significantly higher number of total MTrPs in all evaluated areas of the quadriceps muscle. In the case group, most of the MTrPs were active and only a few were latent, whereas in the control group, as expected, only latent MTrPs were found. In GM, cases had a significantly higher number of total MTrPs in only one area (distal GM), and most MTrPs in this area
were active. It was surprising to find any active MTrPs in GM as this pain referral pattern was not described by Travell and Simons (1992). Also, Roach (Roach et al., 2013) reported a significantly higher prevalence of MTrPs in the GM and QL (quadratus lumborum) in subjects with AKP; however, they found only latent MTrPs in those muscles. Logic summation of MTrPs according to muscles studied allowed us to see some additional patterns. There is clinical importance in summarizing the areas into muscles, even if active MTrPs are not the direct source of AKP. An MTrP (active or latent) in one of the muscles may lead to unbalanced muscle activation in the affected leg. This may be due to an inconsistent muscle activation pattern and reduced efficiency of reciprocal inhibition as has been shown by numerous previous studies that examined the effect of MTrPs on muscle activation (Ibarra et al., 2011; Lucas, 2008; Lucas et al., 2010, 2007). We found MTrPs in all four muscles in the case group. However, the number of thigh muscles with MTrPs appeared to vary among subjects. MTrPs were most frequently located in the VM and VL muscles (nearly in half of the subjects in the case group). This is in accord with one of the theories that claims that AKP occurs due to an extensor mechanism weakness (Boling et al., 2009; Lankhorst et al., 2012) as Celik and Yelden found that patients with latent MTrPs have been shown to be weak compared to controls (Celik and Yeldan, 2011). Furthermore, some authors agree that AKP could be caused by an imbalanced timing between the vastus muscles (Cowan et al., 2002, 2001; Van Tiggelen et al., 2009; Witvrouw et al., 1996), although this claim has recently been questioned (Pattyn et al., 2013). Another established theory contends that quadriceps tightness and decreased flexibility may be a cause of AKP (Pappas and Wong-Tom, 2012; Piva et al., 2005; Witvrouw et al., 2000), even though these theories have not yet included MTrPs as a possible cause of AKP. We assume that as MTrPs can alter motor activation patterns and affect strength in muscles (Lucas et al., 2010), so MTrPs in RF, VM, and VL can lead to weakness and imbalanced activation timing of the extensor mechanism of the knee. These results are consistent with the
Table 4 Comparison of MTrP by limb, controls Rt. Vs. cases affected.
Latent MTrP Active MTrP Total MTrP
Rt. Limb Controls (N ¼ 32)
Affected Limb cases (N ¼ 32)
Comparison Rt vs. affected*
2 (6.3%) 0 2 (6.3%)
7 (21.2%) 25 (75.8%) 26 (78.8%)
c2 ¼ 3.049, p ¼ 0.14 c2¼39.394, p¼0.0001 c2¼34.862, p¼0.0001
a Results of chi-square test; Rt-right; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
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Table 5 Correlations between myofascial scores (number of trigger points) and WOMAC questioners. Sum of all Latent MTrPs
Sum of all Active MTrPs
Total MTrPs
WOMAC Pain
Spearman P value
0.003 0.986
0.241 0.176
0.238 0.182
WOMAC Stiffness
Spearman P value
0.105 0.561
0.109 0.546
0.120 0.507
WOMAC Disability
Spearman P value
0.089 0.622
0.336 0.056
0.362 0.039
a Results of Spearman's correlation. Correlation Coefficient- R and p value Sig. (2-tailed); MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points.
Fig. 1. Scatterplot of WOMAC disability versus total MTrPs. The regression line shows a weak positive correlation.
results of MTrP prevalence that Smith (2012) presented in quadriceps femoris (QF) muscle group. In Smith's study, MTrPs were noted in 93% of 80 patients with AKP. The most prevalent MTrP was in VM (64%), followed by VL (34%) and vastus intermedius in 28% of the patients. MTrPs have also been found in other muscle groups (hamstrings and adductors). Dippenaar et al. (2008) examined subjects with AKP and found MTrPs in all four components of the QF. 95% of the 80 examined subjects had active and/or latent MTrPs and 46% had active MTrPs in the QF muscle. The most common locations of active MTrPs were the mid-belly of the VL muscle (r ¼ 0.87, Spearman's rank correlation), a distal muscular portion of the VL (r ¼ 0.72), and a distal muscular portion of the VM (r ¼ 0.41). Both of those studies did not have a control group. Logic summation over the entire evaluated limb gives an overview of the findings. 78% of subjects in the experimental group demonstrated at least one MTrP compared with the 6.3% of the control group. These high numbers of MTrPs, mostly active MTrPs, leave little doubt that there is a strong association between MTrPs and AKP. Associations between active MTrPs and musculoskeletal pain have also been found in other areas and conditions. For example, neck pain, tension headache, elbow or shoulder pain, and knee osteoarthritis (Bajaj et al., 2001; Dor and Kalichman, 2017;
ndez-de-las-Pen ~ as et al., 2007a,b; Sergienko and Kalichman, Ferna 2015; Shmushkevich and Kalichman, 2013). Additional studies may determine whether myofascial pain and AKP co-exist or whether one causes the other. Either way, we believe that MTrP evaluation should be included in a routine clinical examination of AKP patients and treatment of the MTrPs may alleviate symptoms both in AKP and osteoarthritis. We found only mild to moderate correlations between total MTrPs and WOMAC disability and between the sum of all points to WOMAC pain and WOMAC disability. This is probably since the WOMAC is better suited to subjects with knee osteoarthritis (and not AKP) or to subjects with a lower intensity of function. We assume that more specific questionnaires that are adapted to young high-intensity functioning subjects (like athletes or soldiers) will better represent their functional level and could be more compatible with the MTrPs prevalence. According to the interventional studies performed in other body areas, treatment focusing on myofascial components appears to be effective in reducing pain and improving function in patients with musculoskeletal symptoms (Ajimsha et al., 2012; Nourbakhsh and Fearon, 2008; Tekin et al., 2013). Additional high-quality randomized controlled trials are essential to evaluate the efficacy of treatment focusing on myofascial components in AKP patients.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
Fig. 2. Visual presentation of total MTrPs (summation of active and latent myofascial trigger points) in cases (N ¼ 33, marked in red) and controls (N ¼ 32, marked in green) in each of the evaluated areas: RF-(6,0), mid VM-(11,0), distal VMO-(11,1), mid VL-(10e0), distal VL-(11,0), anterolateral GM-(2,0), post GM-(8,2) and distal GM-(9,0), respectively; statistically significant (p < 0.05) differences marked bold. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
4.1. Study limitations The cross-sectional design of our study does not allow for establishing a cause-effect relationship between MTrP prevalence and AKP. MTrPs in the hip and thigh muscles may be part the AKP etiology, or the AKP may be a cause of MTrPs in muscles which later may mediate the patients’ knee pain. In addition, both aforementioned paths are also possible.
The most relevant muscles to look for MTrPs in patients with AKP is VM and VL. The WOMAC questionnaire is less suitable for AKP assessment in young patients. Funding sources This work was supported by the Milgrom family support fund at the Hebrew University of Jerusalem, Israel.
5. Conclusions Conflicts of interest Subjects with AKP have a higher prevalence of MTrPs (summation of active and latent) than controls. The highest prevalence of MTrPs was found in mid and distal VM and distal VL. Most AKP subjects (78.8%) had at least one MTrP in the evaluated limb whereas only 6.3% of controls had any MTrPs in the evaluated limb. VM and VL are more related to AKP than other evaluated muscles, MTrPs were found in those muscles in nearly half of the case group subjects. Active MTrPs seem to be more important than latent ones, as they refer pain to the anterior knee area and are found in higher prevalence among AKP subjects. These high numbers indicate that soft tissue and MTrPs may play an important role in AKP. This study should be extended to different populations with different age and activity patterns. Also, it is recommended to include calf muscles and hamstrings in further studies due to their biomechanical relationship to AKP. Simons et al. (1999) described that adductor longus and brevis could also cause AKP, therefore, these muscles might also be included in the further research.
None. Authors contributions E. Rozenfeld designed the study, collected data and drafted the manuscript as part of his Master's thesis. A. S. Finestone & L. Kalichman developed the concept of the study, supervised the design, analysis, and interpretation of data and revised the manuscript. U. Moran helped design the study, took part in data acquisition and in critical revision of the article. E. Damri took part in data-acquisition and critical revision of the article. All authors discussed the results and commented on the manuscript. Acknowledgements
Clinical relevance Myofascial pain syndrome and MTrPs should be considered when treating for AKP.
We would like to thank our colleagues, Giora Khayutin, Rotem Kadosh, Daniella Lever, and Nabil Khir for their assistance in data collection and the Milgrom family support fund at the Milgrom
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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Original Research
The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients+ Evgeni Rozenfeld a, b, *, Aharon S. Finestone c, Uria Moran a, Elad Damri a, b, Leonid Kalichman b a
Israel Defense Force, Medical Corps, Israel Department of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel c Assaf HaRofeh Medical Center, Zeriffin, Affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 May 2019 Accepted 9 May 2019
Background: Anterior knee pain (AKP) is a widespread problem among young athletes and soldiers. There are many theories on the etiology of AKP but there is little reference to myofascial trigger points (MTrPs) as a possible contributor. Aim: To evaluate the association between AKP and prevalence of active and latent MTrPs in the hip and thigh muscles in soldiers. Methods: A cross-sectional study was conducted in the Beer-Sheva military outpatient physical therapy clinic. Subjects were 42 men and 23 women referred for physical therapy, 33 with a diagnosis of AKP (cases) and 32 with upper limb complaints (without AKP, controls). All subjects underwent physical evaluation by an examiner blinded to their identity and medical condition. The following muscles were assessed bilaterally for active or latent MTrPs: rectus femoris (proximal), vastus medialis (middle and distal), vastus lateralis (middle and distal) and gluteus medius (anterior, posterior and distal). Results: In six out of eight areas, the cases had a higher prevalence of total active and latent MTrPs than the controls. When summarizing MTrPs by muscle, cases had significantly more MTrPs than controls in each muscle. The largest difference was found in vastus medialis and vastus lateralis; nearly half of the cases had MTrPs in these muscles. Conclusions: Subjects with AKP have a greater prevalence of MTrPs in their hip and thigh muscles than controls, indicating an association between MTrPs and AKP. Further research is necessary to determine whether MTrPs are the cause or the consequence of AKP. © 2019 Elsevier Ltd. All rights reserved.
Keywords: Myofascial trigger points Anterior knee pain Prevalence
1. Introduction The knee is one of the most common sites of injury in athletes and recruits and patellofemoral or anterior knee pain (AKP) constitutes nearly 25% of injuries to the knee (Taunton and Ryan, 2002). AKP is found in high prevalence among military personnel. Studies have found that 12e15% of army recruits worldwide complained of AKP(Boling et al., 2010; Milgrom et al., 1991). Many theories have
+ Results of this study were presented during 8th Conference of International Academy of Manual Musculoskeletal Medicine, Padua, Italy, November 2016. * Corresponding author. Department of Physical Therapy, Recanati School for Community Health Professions, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel. E-mail address: [email protected] (E. Rozenfeld).
been proposed to explain the etiology of AKP, including excessive mechanical loading and chemical irritation of local nerve endings (Dye, 1996; LaBella, 2004), malalignment of the patella relative to the femoral trochlea, ischemia in the lateral retinaculum, overuse, and muscular imbalance (Sanchis-Alfonso, 2008). In general, the literature suggests multifactorial etiology of AKP (Hiemstra et al., 2014). None of these theories include a myofascial origin for AKP. Nevertheless, several studies indicate that Myofascial trigger points (MTrPs) can be associated with other knee problems (Alburquerque-García et al., 2015; Torres-Chica et al., 2014). Myofascial pain syndrome is a common form of somatic pain arising from muscles (Borg-Stein and Simons, 2002). MTrPs are the main component of this syndrome (Chang-Zern Hong, 2006; Gerwin, 2010; Simons et al., 1999), defined as a hyperirritable spots within a palpable taut band of a skeletal muscle that is painful on
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Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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List of abbreviations BMI GM MTrP QF RF VL VM
body mass index gluteus medius myofascial trigger point quadratus femoris rectus femoris vastus lateralis vastus medialis
compression, stretch, or overload, and that gives rise to a referred pain (Simons et al., 1999). The diagnosis of MTrPs is a clinical skill based on palpation, following the diagnostic criteria established by Simons et al. (1999) and Gerwin et al. (1997). Published studies have reported poor to good reliability for MTrPs palpation (Al-Shenqiti and Oldham, 2005; Bron et al., 2007; Gerwin et al., 1997; Hsieh et al., 2000; Nice et al., 1992; Njoo and Van Der Does, 1994; Zuil-Escobar et al., 2016). Lately, Rozenfeld et al. (2017) found that MTrP palpation is a moderately reliable diagnostic tool in the hip and thigh muscles and it can be used in clinical practice and research. Another recent study by Walsh et al. (2017)suggests that palpation is a reliable method for locating MTrPs in the VM and VL. Numerous studies on the upper limb muscles have shown a significantly greater number of active MTrPs on the painful side (Alburquerque-Sendín et al., 2013; Bron et al., 2011; Ge et al., 2008). However, very few studies have explored the association between MTrPs and pain in the lower limb, and only two looked for MTrPs in hip and thigh muscles in patients with AKP (Dippenaar et al., 2008; Smith, 2012). A recently published review suggested that there is initial evidence to the assumption that MTrPs may play a role in pain and disability of patients with knee osteoarthritis (Dor and Kalichman, 2017). The aims of this study were: To evaluate the association between AKP and prevalence of active and latent MTrPs in hip and thigh muscles in soldiers. To evaluate the association between the number of MTrPs and severity of AKP complaints. Hypotheses: MTrPs are more prevalent in the hip and thigh muscles in soldiers complaining of AKP, than in those without AKP. In subjects with AKP, the number of MTrPs is associated with the more severe condition (as reflected by the Western Ontario and McMaster Universities Arthritis Index (WOMAC).
their study of MTrPs in the hip in AKP patients and by other casecontrol studies on the prevalence of myofascial pain (Carnero et al., 2008). Inclusion criteria for the case group were: Age between 18 and 30 and referral for physical therapy by a physician due to AKP present for >6 weeks. (i.e. retropatellar pain which increased in weight-bearing activities such as jumping, running, squatting, and going up or down stairs or in prolonged sitting with flexed knees), and a positive patellar grinding test. Exclusion criteria were: Any severe medical condition that may be a contraindication for physical treatment; participation in another interventional clinical trial; history of major trauma or operation in lower limb; positive findings in the examination of knee ligaments; menisci; bursa; iliotibial band; patellar tendons and their insertions; knee pain originating from osteoarthritis; history of major psychiatric or neurological illness; fibromyalgia or other systemic rheumatic diseases; pregnancy. None of the subjects had met the examiner before the study. Ethics: All subjects received an explanation about the study and signed an informed consent form. The study was approved by the Israel Defense Forces ethical review board (Approval No. 1427e2014). Evaluation procedure: Each subject completed the demographic questionnaire and WOMAC. In subjects with bilateral pain, the questionnaires referred to the more painful knee. They had a complete orthopedic evaluation, followed by an examination of 4 muscles of each leg for MTrPs. The examiner that performed the MTrP evaluation was a physical therapist with at least 6 years of practice including myofascial evaluation and treatment. The examiner was blinded to subjects' identities and medical condition. Demographic data on age, sex, occupation, leisure physical activity, health history, data on present disease (onset of symptoms, previous treatments etc.), weight and height were collected. WOMAC questionnaire: Each participant was asked to fill the Hebrew version of the WOMAC questionnaire. WOMAC is a disease-specific, purpose-built, high-performance instrument for evaluating pain, joint stiffness, and function in knee and hip osteoarthritis clinical trials. It has been extensively validated and is recommended by the Osteoarthritis Research Society. The WOMAC questionnaire has a visual analog scale ranging from 0 to 10 cm, where 0 cm indicates no pain or limitation in function and 10 cm indicates the most severe pain or limitation in function. It has 3 subscales: pain (5 items) stiffness (2 items) and function (17 items). All the subscales have high test-retest reliability, and validation studies have shown high correlations with other indices probing the same dimensions (B, 2015; Bellamy et al., 1988; McConnell et al., 2001). Furthermore, the Hebrew version of WOMAC was found to be reliable and valid for use in Israeli patients with knee OA (Wigler et al., 1999). Reliability: intra-class coefficients ranged from 0.12 to 0.69 (p < 0.01). MTrP assessment: The examiners performed an evaluation of MTrPs using a flat palpation technique, according to the diagnostic criteria established by Simons et al. (1999) to identify the following:
2. Methods Design: Observational, exploratory, cross-sectional study. Prevalence of MTrPs was evaluated in patients with AKP and matched controls without knee pain. Setting: Physical Therapy Department, Military outpatient clinic, Beer Sheva, Israel. Subjects: We recruited 65 soldiers and officers (42 men and 23 women) who were referred for physical therapy due to various medical conditions. Cases (N ¼ 33) had been referred for physical therapy with a diagnosis of AKP and controls (N ¼ 32) had been referred with upper limb complaints and had no complaints about knee pain. A similar sample size was used by Roach et al. (2013) in
The presence of a taut band. The presence of a tender spot on the taut band during palpation. Reproduction of referred pain during MTrP compression. All criteria were scored dichotomously, as presence or absence of each criterion. If the examiner was unsure of the result, he was instructed to score that specific criterion as absent. All subjects were asked if the palpation caused referred pain and if the referred pain was relevant to their complaint. Prior to the blinded examination, controls (without knee pain) had been instructed to answer the question on the relevance of the referred pain negatively. Definition of the active and latent MTrPs was made by
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
summation of the diagnostic criteria. A point was considered as MTrP when a taut band, tenderness, and referred pain were all present. If the subject answered that the referred pain was relevant to their complaints the MTrP was labeled as active. If not, the MTrP was considered latent. The evaluation was performed in 8 areas of four muscles in both legs. Vastus lateralis (VL): middle and distal, vastus medialis (VM): middle and distal, gluteus medius (GM): anterior, posterior and distal, and rectus femoris (RF). These muscles were chosen as MTrPs in these areas refer pain to the anterior knee region (Travell and Simons, 1992) and can potentially cause AKP due to muscle weakness and imbalance (Barton et al., 2013; Meira and Brumitt, 2011; Prins and van der Wurff, 2009). There are more muscles that refer to the knee, yet based on the researchers’ clinical experience, only those areas were included. The intra- and inter-rater reliability of the aforementioned MTrP detection has been evaluated and reported (Rozenfeld et al., 2017). 2.1. Statistical analysis All statistical analysis was performed using the SPSS statistical package (Version 17). Significance levels were set at p < 0.05. Descriptive statistics were used to characterize the study sample. We used independent T-test and c2 test to compare demographic characteristics and WOMAC results between cases and controls. To compare the prevalence of MTrPs between subjects with and without AKP a c2 test was used. The measuring scale was nominal. Since significant differences were not found in the prevalence of MTrPs between both legs in the control group (McNemar's test was p > 0.05 between left and right legs in all cases), it was decided to compare MTrPs prevalence in the right leg of controls, to the affected leg of cases (the more painful leg was used in subjects with AKP). To evaluate the association between MTrPs prevalence and WOMAC, Spearman's correlation was used. A special MTrP score summarizing the MTrP prevalence in all areas of each subject was created. The score ranged from 0 to 8 (0 means that there are no MTrPs in any of the areas that were evaluated, whereas 8 means that there was an MTrP in each of those areas). Since an active MTrP is composed of latent MTrPs together with “referred pain relevant to patient complaints”, to avoid double scoring it was determined that if an active MTrP was positive, then the latent MTrP would be marked as negative. This way, only one of the points can be positive at a given time. Data on two types of MTrPs are presented in the results: active and latent. The total MTrPs were also calculated (the summation of active and latent MTrPs) and presented. 3. Results Study participants’ characteristics are summarized in Table 1. In total 65 subjects (18 males and 15 females in the case group and 24
3
males and 8 females in the control group) met the inclusion criteria and agreed to participate in this study. There was no significant difference between the groups in any of the demographic parameters (age, BMI, service period, sex, and type of military service). Table 2 presents the comparison between the MTrP prevalence in the right leg of the controls to the affected leg of the cases in all studied areas. Data are presented according to the prevalence of MTrP in each of eight muscle areas. For each area, data on three types of MTrP are presented (active, latent and total MTrP). In six out of eight areas, cases had a higher prevalence of total MTrPs than controls. The difference was significant for all areas except anterolateral and posterior GM. The strongest difference was in mid VM and distal VL (11, 33.3%, total MTrPs in cases vs. 0 in controls; c2 ¼ 12.840, d.f. ¼ 1, p ¼ 0.0001). A logic summation of MTrPs by muscles was performed, which is to say that if one of the areas in the muscle had a MTrP, then the muscle was considered positive for MTrPs. For example, if middle VMO had an active MTrP, whereas distal VM did not, VM was marked as positive for active MTrP. As shown in Table 3, cases had
Table 2 Comparison of MTrP prevalence between right leg in the control group (N ¼ 32) and the affected leg in case group (N ¼ 33). MTrPs
Right
Affected
Rt vs. Affected**
Latent MTrP RF Active MTrP RF Total MTrP RF
0 0 0
1 (3.0%) 5 (15.2%) 6 (18.2%)
c2 ¼ 0.985, p ¼ 1.00 c2 ¼ 5.253, p ¼ 0.05 c2¼6.410, p¼0.02
Latent MTrP Middle VM Active MTrP Middle VM Total MTrP Middle VM
0 0 0
0 11 (33.3%) 11 (33.3%)
c2¼12.840, p¼0.0001 c2¼12.840, p¼0.0001
Latent MTrP Distal VM Active MTrP Distal VM Total MTrP Distal VM
1 (3.1%) 0 1 (3.1%)
0 11 (33.3%) 11 (33.3%)
c2 ¼ 1.047, p ¼ 0.49 c2¼12.840, p¼0.0001 c2¼9.849, p¼0.002
Latent MTrP Middle VL Active MTrP Middle VL Total MTrP Middle VL
0 0 0
2 (6.1%) 8 (24.2%) 10 (30.3%)
c2 ¼ 2.001, p ¼ 0.49 c2¼8.846, p¼0.005 c2¼11.460, p¼0.001
Latent MTrP Distal VL Active MTrP Distal VL Total MTrP Distal VL
0 0 0
0 11 (33.3%) 11 (33.3%)
c2¼12.840, p¼0.0001 c2¼12.840, p¼0.0001
Latent MTrP Anterolateral GM Active MTrP Anterolateral GM Total MTrP Anterolateral GM
0 0 0
2 (6.1%) 0 2 (6.1%)
c2 ¼ 2.001, p ¼ 0.49
Latent MTrP Posterior GM Active MTrP Posterior GM Total MTrP Posterior GM
2 (6.3%) 0 2 (6.3%)
2 (6.1%) 6 (18.2%) 8 (24.2%)
c2 ¼ 0.001, p ¼ 1.00 c2¼6.410, p¼0.024 c2 ¼ 4.040, p ¼ 0.08
Latent MTrP Distal GM Active MTrP Distal GM Total MTrP Distal GM
0 0 0
3 (9.1%) 6 (18.2%) 9 (27.3%)
c2 ¼ 3.050, p ¼ 0.23 c2¼6.410, p¼0.024 c2¼10.130, p¼0.002
c2 ¼ 2.001, p ¼ 0.49
a Results of chi-square test; RT-right, LT-left; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; RF-rectus femoris, VM-vastus medialis, VL-vastus lateralis, GM-gluteus medius; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
Table 1 Descriptive statistics of cases and controls. Characteristics
Case group (N ¼ 33)
Control group (N ¼ 32)
Comparison*
Age (years) BMI (kg/m2) Service period (months)
20.49 ± 2.00 23.60 ± 3.35 16.39 ± 15.6
20.98 ± 2.11 23.35 ± 4.17 22.13 ± 13.91
T ¼ 0.960, p ¼ 0.34 T ¼ 0.268, p ¼ 0.78 T ¼ 1.561, p ¼ 0.12
Sex (Males) Type of service
18 (54.5%) 10 (30.3%) 14 (42.4%) 9 (27.3%)
24 (75%) 12 (37.5%) 6 (18.8%) 14 (43.8%)
c2 ¼ 2.973, d.f. ¼ 1, p ¼ 0.07 c2 ¼ 4.454, d.f. ¼ 2, p ¼ 0.10
Comparison**
a
Results of Independent T-Test;
Combat Support Office b
Results of chi-square test; BMI-body mass index.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
Table 3 Comparison of MTrP by muscles, control Rt. Vs. cases affected. Muscle
Right limb controls (N ¼ 32)
Affected limb cases (N ¼ 33)
Comparison Right vs. affected*
RF
Latent MTrP Active MTrP Total MTrP
0 0 0
1 (3.0%) 5 (15.2%) 6 (18.2%)
c2 ¼ 0.985, p ¼ 1.00 c2 ¼ 5.253, p ¼ 0.05 c2¼6.410, p¼0.024
VM
Latent MTrP Active MTrP Total MTrP
1 (3.1%) 0 1 (3.1%)
0 15 (45.5%) 15 (45.5%)
c2 ¼ 1.047, p ¼ 0.49 c2¼18.909, p¼0.0001 c2¼15.687, p¼0.0001
VL
Latent MTrP Active MTrP Total MTrP
0 0 0
2 (6.1%) 16 (48.5%) 16 (48.5%)
c2 ¼ 2.001, p ¼ 0.49 c2¼20.587, p¼0.0001 c2¼20.587, p¼0.0001
GM
Latent MTrP Active MTrP Total MTrP
2 (6.3%) 0 2 (6.3%)
5 (15.2%) 7 (21.2%) 12 (36.4%)
c2 ¼ 1.340, p ¼ 0.42 c2¼7.607, p¼0.01 c2¼8.718, p¼0.003
a Results of chi-square test; RF-rectus femoris, VM-vastus medialis, VL-vastus lateralis, GM-gluteus medius; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
significantly more total MTrPs than controls in all evaluated muscles. The largest prevalence of total MTrPs was found in VL muscle; 16 (48.5%) total MTrPs in the case group, whereas in the control group there were 0 total MTrPs (c2 ¼ 20.587, d.f. ¼ 1, p ¼ 0.0001). The smallest, yet significant difference was in RF muscle with 6 (18.2%) total MTrPs in cases and 0 total MTrPs in controls (c2 ¼ 6.410, d.f. ¼ 1, p ¼ 0.024). When summarizing MTrPs in the entire limb (if one of the evaluated areas had a positive MTrP, then the whole limb was considered positive for MTrPs) (Table 4), 78.8% of the subjects in the case group had at least one MTrP in the evaluated limb whereas only 6.3% of the subjects in the control group had any MTrP in the evaluated limb (c2 ¼ 34.862, d.f. ¼ 1, p ¼ 0.0001). Table 5 presents the Spearman's correlations between the MTrP score and WOMAC, results while Fig. 1 shows a scatterplot of WOMAC disability subscale versus the total MTrPs. The sum of all latent MTrPs and all active MTrPs showed no correlation to any of the WOMAC subscales. The total MTrPs showed a significant positive correlation to WOMAC disability (r ¼ 0.36, p ¼ 0.04) and there was no correlation to any other score. 4. Discussion Only a few previous studies suggested MTrPs as a potential cause of AKP (Roach et al., 2013; Smith, 2012). This is the first extensive report on the prevalence of MTrPs in hip and thigh muscles in patients with AKP. This study demonstrates a significant difference between cases and controls in the prevalence of MTrPs in most studied areas (Fig. 2). When we compared the affected leg in cases to the right leg in controls we found that cases had a significantly higher number of total MTrPs in all evaluated areas of the quadriceps muscle. In the case group, most of the MTrPs were active and only a few were latent, whereas in the control group, as expected, only latent MTrPs were found. In GM, cases had a significantly higher number of total MTrPs in only one area (distal GM), and most MTrPs in this area
were active. It was surprising to find any active MTrPs in GM as this pain referral pattern was not described by Travell and Simons (1992). Also, Roach (Roach et al., 2013) reported a significantly higher prevalence of MTrPs in the GM and QL (quadratus lumborum) in subjects with AKP; however, they found only latent MTrPs in those muscles. Logic summation of MTrPs according to muscles studied allowed us to see some additional patterns. There is clinical importance in summarizing the areas into muscles, even if active MTrPs are not the direct source of AKP. An MTrP (active or latent) in one of the muscles may lead to unbalanced muscle activation in the affected leg. This may be due to an inconsistent muscle activation pattern and reduced efficiency of reciprocal inhibition as has been shown by numerous previous studies that examined the effect of MTrPs on muscle activation (Ibarra et al., 2011; Lucas, 2008; Lucas et al., 2010, 2007). We found MTrPs in all four muscles in the case group. However, the number of thigh muscles with MTrPs appeared to vary among subjects. MTrPs were most frequently located in the VM and VL muscles (nearly in half of the subjects in the case group). This is in accord with one of the theories that claims that AKP occurs due to an extensor mechanism weakness (Boling et al., 2009; Lankhorst et al., 2012) as Celik and Yelden found that patients with latent MTrPs have been shown to be weak compared to controls (Celik and Yeldan, 2011). Furthermore, some authors agree that AKP could be caused by an imbalanced timing between the vastus muscles (Cowan et al., 2002, 2001; Van Tiggelen et al., 2009; Witvrouw et al., 1996), although this claim has recently been questioned (Pattyn et al., 2013). Another established theory contends that quadriceps tightness and decreased flexibility may be a cause of AKP (Pappas and Wong-Tom, 2012; Piva et al., 2005; Witvrouw et al., 2000), even though these theories have not yet included MTrPs as a possible cause of AKP. We assume that as MTrPs can alter motor activation patterns and affect strength in muscles (Lucas et al., 2010), so MTrPs in RF, VM, and VL can lead to weakness and imbalanced activation timing of the extensor mechanism of the knee. These results are consistent with the
Table 4 Comparison of MTrP by limb, controls Rt. Vs. cases affected.
Latent MTrP Active MTrP Total MTrP
Rt. Limb Controls (N ¼ 32)
Affected Limb cases (N ¼ 32)
Comparison Rt vs. affected*
2 (6.3%) 0 2 (6.3%)
7 (21.2%) 25 (75.8%) 26 (78.8%)
c2 ¼ 3.049, p ¼ 0.14 c2¼39.394, p¼0.0001 c2¼34.862, p¼0.0001
a Results of chi-square test; Rt-right; MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points; for all results degrees of freedom (df ¼ 1); statistically significant (p < 0.05) differences marked bold.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
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Table 5 Correlations between myofascial scores (number of trigger points) and WOMAC questioners. Sum of all Latent MTrPs
Sum of all Active MTrPs
Total MTrPs
WOMAC Pain
Spearman P value
0.003 0.986
0.241 0.176
0.238 0.182
WOMAC Stiffness
Spearman P value
0.105 0.561
0.109 0.546
0.120 0.507
WOMAC Disability
Spearman P value
0.089 0.622
0.336 0.056
0.362 0.039
a Results of Spearman's correlation. Correlation Coefficient- R and p value Sig. (2-tailed); MTrP- myofascial trigger point, Total MTrP- summation of active and latent myofascial trigger points.
Fig. 1. Scatterplot of WOMAC disability versus total MTrPs. The regression line shows a weak positive correlation.
results of MTrP prevalence that Smith (2012) presented in quadriceps femoris (QF) muscle group. In Smith's study, MTrPs were noted in 93% of 80 patients with AKP. The most prevalent MTrP was in VM (64%), followed by VL (34%) and vastus intermedius in 28% of the patients. MTrPs have also been found in other muscle groups (hamstrings and adductors). Dippenaar et al. (2008) examined subjects with AKP and found MTrPs in all four components of the QF. 95% of the 80 examined subjects had active and/or latent MTrPs and 46% had active MTrPs in the QF muscle. The most common locations of active MTrPs were the mid-belly of the VL muscle (r ¼ 0.87, Spearman's rank correlation), a distal muscular portion of the VL (r ¼ 0.72), and a distal muscular portion of the VM (r ¼ 0.41). Both of those studies did not have a control group. Logic summation over the entire evaluated limb gives an overview of the findings. 78% of subjects in the experimental group demonstrated at least one MTrP compared with the 6.3% of the control group. These high numbers of MTrPs, mostly active MTrPs, leave little doubt that there is a strong association between MTrPs and AKP. Associations between active MTrPs and musculoskeletal pain have also been found in other areas and conditions. For example, neck pain, tension headache, elbow or shoulder pain, and knee osteoarthritis (Bajaj et al., 2001; Dor and Kalichman, 2017;
ndez-de-las-Pen ~ as et al., 2007a,b; Sergienko and Kalichman, Ferna 2015; Shmushkevich and Kalichman, 2013). Additional studies may determine whether myofascial pain and AKP co-exist or whether one causes the other. Either way, we believe that MTrP evaluation should be included in a routine clinical examination of AKP patients and treatment of the MTrPs may alleviate symptoms both in AKP and osteoarthritis. We found only mild to moderate correlations between total MTrPs and WOMAC disability and between the sum of all points to WOMAC pain and WOMAC disability. This is probably since the WOMAC is better suited to subjects with knee osteoarthritis (and not AKP) or to subjects with a lower intensity of function. We assume that more specific questionnaires that are adapted to young high-intensity functioning subjects (like athletes or soldiers) will better represent their functional level and could be more compatible with the MTrPs prevalence. According to the interventional studies performed in other body areas, treatment focusing on myofascial components appears to be effective in reducing pain and improving function in patients with musculoskeletal symptoms (Ajimsha et al., 2012; Nourbakhsh and Fearon, 2008; Tekin et al., 2013). Additional high-quality randomized controlled trials are essential to evaluate the efficacy of treatment focusing on myofascial components in AKP patients.
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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E. Rozenfeld et al. / Journal of Bodywork & Movement Therapies xxx (xxxx) xxx
Fig. 2. Visual presentation of total MTrPs (summation of active and latent myofascial trigger points) in cases (N ¼ 33, marked in red) and controls (N ¼ 32, marked in green) in each of the evaluated areas: RF-(6,0), mid VM-(11,0), distal VMO-(11,1), mid VL-(10e0), distal VL-(11,0), anterolateral GM-(2,0), post GM-(8,2) and distal GM-(9,0), respectively; statistically significant (p < 0.05) differences marked bold. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
4.1. Study limitations The cross-sectional design of our study does not allow for establishing a cause-effect relationship between MTrP prevalence and AKP. MTrPs in the hip and thigh muscles may be part the AKP etiology, or the AKP may be a cause of MTrPs in muscles which later may mediate the patients’ knee pain. In addition, both aforementioned paths are also possible.
The most relevant muscles to look for MTrPs in patients with AKP is VM and VL. The WOMAC questionnaire is less suitable for AKP assessment in young patients. Funding sources This work was supported by the Milgrom family support fund at the Hebrew University of Jerusalem, Israel.
5. Conclusions Conflicts of interest Subjects with AKP have a higher prevalence of MTrPs (summation of active and latent) than controls. The highest prevalence of MTrPs was found in mid and distal VM and distal VL. Most AKP subjects (78.8%) had at least one MTrP in the evaluated limb whereas only 6.3% of controls had any MTrPs in the evaluated limb. VM and VL are more related to AKP than other evaluated muscles, MTrPs were found in those muscles in nearly half of the case group subjects. Active MTrPs seem to be more important than latent ones, as they refer pain to the anterior knee area and are found in higher prevalence among AKP subjects. These high numbers indicate that soft tissue and MTrPs may play an important role in AKP. This study should be extended to different populations with different age and activity patterns. Also, it is recommended to include calf muscles and hamstrings in further studies due to their biomechanical relationship to AKP. Simons et al. (1999) described that adductor longus and brevis could also cause AKP, therefore, these muscles might also be included in the further research.
None. Authors contributions E. Rozenfeld designed the study, collected data and drafted the manuscript as part of his Master's thesis. A. S. Finestone & L. Kalichman developed the concept of the study, supervised the design, analysis, and interpretation of data and revised the manuscript. U. Moran helped design the study, took part in data acquisition and in critical revision of the article. E. Damri took part in data-acquisition and critical revision of the article. All authors discussed the results and commented on the manuscript. Acknowledgements
Clinical relevance Myofascial pain syndrome and MTrPs should be considered when treating for AKP.
We would like to thank our colleagues, Giora Khayutin, Rotem Kadosh, Daniella Lever, and Nabil Khir for their assistance in data collection and the Milgrom family support fund at the Milgrom
Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010
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Please cite this article as: Rozenfeld, E et al., The prevalence of myofascial trigger points in hip and thigh areas in anterior knee pain patients, Journal of Bodywork & Movement Therapies, https://doi.org/10.1016/j.jbmt.2019.05.010