Risk factors for patellofemoral pain: a systematic review and meta-analysis.

BACKGROUND: Patellofemoral pain (PFP) is a prevalent condition commencing at various points throughout life. We aimed to provide an evidence synthesis concerning predictive variables for PFP, to aid development of preventative interventions. METHODS: We searched Medline, Web of Science and SCOPUS until February 2017 for prospective studies investigating at least one potential risk factor for future PFP. Two independent reviewers appraised methodological quality using the Newcastle-Ottawa Scale. We conducted meta-analysis where appropriate, with standardised mean differences (SMD) and risk ratios calculated for continuous and nominal scaled data. RESULTS: This review included 18 studies involving 4818 participants, of whom 483 developed PFP (heterogeneous incidence 10%). Three distinct subgroups (military recruits, adolescents and recreational runners) were identified. Strong to moderate evidence indicated that age, height, weight, body mass index (BMI), body fat and Q angle were not risk factors for future PFP. Moderate evidence indicated that quadriceps weakness was a risk factor for future PFP in the military, especially when normalised by BMI (SMD -0.69, CI -1.02, -0.35). Moderate evidence indicated that hip weakness was not a risk factor for future PFP (multiple pooled SMDs, range -0.09 to -0.20), but in adolescents, moderate evidence indicated that increased hip abduction strength was a risk factor for future PFP (SMD 0.71, CI 0.39, 1.04). CONCLUSIONS: This review identified multiple variables that did not predict future PFP, but quadriceps weakness in military recruits and higher hip strength in adolescents were risk factors for PFP. Identifying modifiable risk factors is an urgent priority to improve prevention and treatment outcomes.

Exercise for treating patellofemoral pain syndrome: an abridged version of Cochrane systematic review.

BACKGROUND: Patellofemoral pain syndrome (PFPS) is a common knee problem characterised by retropatellar or peripatellar pain, which particularly affects adolescents and young adults. Exercise therapy is often prescribed. AIM: To assess the effects of exercise therapy in people with PFPS. DESIGN: Systematic review. SETTING: All settings. POPULATION: Adolescents and adults with PFPS. METHODS: A search was performed in nine databases up to May 2014, including the Cochrane Register, MEDLINE and EMBASE. Randomised and quasi-randomised trials evaluating the effect of exercise therapy in adolescents and adults with PFPS were considered for inclusion. Two review authors independently selected trials, extracted data and assessed risk of bias. RESULTS: In total, 31 trials including 1690 participants were included in this review, of which most were at high risk of performance bias and detection bias due to lack of blinding. The included studies provided evidence for: exercise therapy versus control; exercise therapy versus other conservative interventions (e.g. taping); and different exercises or exercise programmes. Pooled data favoured exercise therapy over control for pain during activity (short term MD -1.46 [-2.39, -0.54]), usual pain (short term estimated MD -1.44 [-2.48,-0.39]), functional ability; (short term estimated MD 12.21 [6.44, 18.09] and long term recovery (RR 1.35 [0.99, 1.84]). Pooled data favoured hip and knee exercise over knee exercises alone for pain during activity (short-term MD -2.20 [3.80, -0.60]) and usual pain (short term MD-1.77 [-2.78,-0.76]). CONCLUSION: This review found very low quality but consistent evidence that exercise therapy for PFPS may result in clinically important reduction in pain and improvement in functional ability, as well as enhancing long-term recovery. There is some very low quality evidence that hip plus knee exercises may be more effective in reducing pain than knee exercise alone. CLINICAL REHABILITATION IMPACT: Very low quality evidence but consistent evidence indicates that exercise therapy benefits patients with PFP. However, there is insufficient evidence to determine the best form of exercise therapy and it is unknown whether this result would apply to all people with PFPS.

Can we predict which patients with patellofemoral pain are more likely to benefit from exercise therapy? A secondary exploratory analysis of a randomized controlled trial.

STUDY DESIGN: Secondary exploratory analysis of a randomized controlled trial comparing supervised exercise therapy to usual care in patients with patellofemoral pain (PFP). OBJECTIVE: To explore which patients with PFP are more likely to benefit from exercise therapy. BACKGROUND: Patellofemoral pain is a common condition for which exercise therapy is effective in reducing pain and improving function. However, not all patients benefit from exercise therapy. METHODS: The present study explored patient characteristics that might interact with treatment effects of PFP in 131 patients treated with usual care or exercise therapy. These characteristics were tested for interaction with treatment in a regression analysis. The primary outcomes were function and pain on activity at a 3-month follow-up. RESULTS: None of the tested variables had a significant interaction with treatment. A positive trend was seen for females with PFP: they were more likely to report higher function scores with exercise therapy than with usual care compared to males with PFP (ß = 12.1; 95% confidence interval: 0.23, 24.0; P = .05). A positive trend was seen for patients with a longer duration of complaints (greater than 6 months); they were more likely to report higher function scores and to have less pain on activity with exercise therapy than with usual care compared to those with a shorter duration of complaints (ß = 12.3; 95% confidence interval: -0.08, 24.7; P = .05 and ß = -1.74; 95% confidence interval: -3.90, 0.43; P = .12, respectively). CONCLUSION: Two factors, sex and duration of complaints, may have a predictive value for response to exercise therapy at 3-month follow-up. Due to the exploratory design of the study, future research should confirm this tendency.

Exercise for treating patellofemoral pain syndrome.

BACKGROUND: Patellofemoral pain syndrome (PFPS) is a common knee problem, which particularly affects adolescents and young adults. PFPS, which is characterised by retropatellar (behind the kneecap) or peripatellar (around the kneecap) pain, is often referred to as anterior knee pain. The pain mostly occurs when load is put on the knee extensor mechanism when climbing stairs, squatting, running, cycling or sitting with flexed knees. Exercise therapy is often prescribed for this condition. OBJECTIVES: To assess the effects (benefits and harms) of exercise therapy aimed at reducing knee pain and improving knee function for people with patellofemoral pain syndrome. SEARCH METHODS: We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (May 2014), the Cochrane Central Register of Controlled Trials (2014, Issue 4), MEDLINE (1946 to May 2014), EMBASE (1980 to 2014 Week 20), PEDro (to June 2014), CINAHL (1982 to May 2014) and AMED (1985 to May 2014), trial registers (to June 2014) and conference abstracts. SELECTION CRITERIA: Randomised and quasi-randomised trials evaluating the effect of exercise therapy on pain, function and recovery in adolescents and adults with patellofemoral pain syndrome. We included comparisons of exercise therapy versus control (e.g. no treatment) or versus another non-surgical therapy; or of different exercises or exercise programmes. DATA COLLECTION AND ANALYSIS: Two review authors independently selected trials based on pre-defined inclusion criteria, extracted data and assessed risk of bias. Where appropriate, we pooled data using either fixed-effect or random-effects methods. We selected the following seven outcomes for summarising the available evidence: pain during activity (short-term: ≤ 3 months); usual pain (short-term); pain during activity (long-term: > 3 months); usual pain (long-term); functional ability (short-term); functional ability (long-term); and recovery (long-term). MAIN RESULTS: In total, 31 heterogeneous trials including 1690 participants with patellofemoral pain are included in this review. There was considerable between-study variation in patient characteristics (e.g. activity level) and diagnostic criteria for study inclusion (e.g. minimum duration of symptoms) and exercise therapy. Eight trials, six of which were quasi-randomised, were at high risk of selection bias. We assessed most trials as being at high risk of performance bias and detection bias, which resulted from lack of blinding.The included studies, some of which contributed to more than one comparison, provided evidence for the following comparisons: exercise therapy versus control (10 trials); exercise therapy versus other conservative interventions (e.g. taping; eight trials evaluating different interventions); and different exercises or exercise programmes. The latter group comprised: supervised versus home exercises (two trials); closed kinetic chain (KC) versus open KC exercises (four trials); variants of closed KC exercises (two trials making different comparisons); other comparisons of other types of KC or miscellaneous exercises (five trials evaluating different interventions); hip and knee versus knee exercises (seven trials); hip versus knee exercises (two studies); and high- versus low-intensity exercises (one study). There were no trials testing exercise medium (land versus water) or duration of exercises. Where available, the evidence for each of seven main outcomes for all comparisons was of very low quality, generally due to serious flaws in design and small numbers of participants. This means that we are very unsure about the estimates. The evidence for the two largest comparisons is summarised here. Exercise versus control. Pooled data from five studies (375 participants) for pain during activity (short-term) favoured exercise therapy: mean difference (MD) -1.46, 95% confidence interval (CI) -2.39 to -0.54. The CI included the minimal clinically important difference (MCID) of 1.3 (scale 0 to 10), indicating the possibility of a clinically important reduction in pain. The same finding applied for usual pain (short-term; two studies, 41 participants), pain during activity (long-term; two studies, 180 participants) and usual pain (long-term; one study, 94 participants). Pooled data from seven studies (483 participants) for functional ability (short-term) also favoured exercise therapy; standardised mean difference (SMD) 1.10, 95% CI 0.58 to 1.63. Re-expressed in terms of the Anterior Knee Pain Score (AKPS; 0 to 100), this result (estimated MD 12.21 higher, 95% CI 6.44 to 18.09 higher) included the MCID of 10.0, indicating the possibility of a clinically important improvement in function. The same finding applied for functional ability (long-term; three studies, 274 participants). Pooled data (two studies, 166 participants) indicated that, based on the 'recovery' of 250 per 1000 in the control group, 88 more (95% CI 2 fewer to 210 more) participants per 1000 recovered in the long term (12 months) as a result of exercise therapy. Hip plus knee versus knee exercises. Pooled data from three studies (104 participants) for pain during activity (short-term) favoured hip and knee exercise: MD -2.20, 95% CI -3.80 to -0.60; the CI included a clinically important effect. The same applied for usual pain (short-term; two studies, 46 participants). One study (49 participants) found a clinically important reduction in pain during activity (long-term) for hip and knee exercise. Although tending to favour hip and knee exercises, the evidence for functional ability (short-term; four studies, 174 participants; and long-term; two studies, 78 participants) and recovery (one study, 29 participants) did not show that either approach was superior. AUTHORS' CONCLUSIONS: This review has found very low quality but consistent evidence that exercise therapy for PFPS may result in clinically important reduction in pain and improvement in functional ability, as well as enhancing long-term recovery. However, there is insufficient evidence to determine the best form of exercise therapy and it is unknown whether this result would apply to all people with PFPS. There is some very low quality evidence that hip plus knee exercises may be more effective in reducing pain than knee exercise alone.Further randomised trials are warranted but in order to optimise research effort and engender the large multicentre randomised trials that are required to inform practice, these should be preceded by research that aims to identify priority questions and attain agreement and, where practical, standardisation regarding diagnostic criteria and measurement of outcome.

Factors associated with patellofemoral pain syndrome: a systematic review.

This review systematically summarises factors associated with patellofemoral pain syndrome (PFPS). A systematic literature search was conducted. Studies including ≥20 patients with PFPS that examined ≥1 possible factor associated with PFPS were included. A meta-analysis was performed, clinical heterogeneous data were analysed descriptively. The 47 included studies examined 523 variables, eight were pooled. Pooled data showed a larger Q-angle, sulcus angle and patellar tilt angle (weighted mean differences (WMD) 2.08; 95% CI 0.64, 3.63 and 1.66; 95% CI 0.44, 2.77 and 4.34; 95% CI 1.16 to 7.52, respectively), less hip abduction strength, lower knee extension peak torque and less hip external rotation strength (WMD -3.30; 95% CI -5.60, -1.00 and -37.47; 95% CI -71.75, -3.20 and -1.43; 95% CI -2.71 to -0.16, respectively) in PFPS patients compared to controls. Foot arch height index and congruence angle were not associated with PFPS. Six out of eight pooled variables are associated with PFPS, other factors associated with PFPS were based on single studies. Further research is required.

Risk factors for patellofemoral pain syndrome: a systematic review.

STUDY DESIGN: Systematic review. OBJECTIVES: To systematically outline the risk factors for patellofemoral pain syndrome (PFPS). BACKGROUND: PFPS is the most commonly diagnosed condition in young individuals with knee complaints. High incidence among athletes suggests a possibility of prevention. The first step toward prevention is identification of possible risk factors. METHODS: Prospective studies that included 20 or more patients with PFPS and examined at least 1 possible risk factor for PFPS were included. An assessment list was applied to evaluate the quality of the studies. A meta-analysis was conducted using a random-effects model. Significant differences were based on calculated mean differences, with matching 95% confidence intervals (CIs). For dichotomous data, odds ratios or relative risks were calculated. RESULTS: Of the 3845 potentially relevant articles, 7 were included in this review. These studies examined a total of 135 variables, and pooling was possible for 13 potential risk factors. The pooled data showed that knee extension peak torques were significantly lower in the PFPS group than in controls. Mean differences in torque, with negative differences reflecting lower means in the PFPS group, were as follows: (a) standardized relative to body weight at 60°/s, -0.24 Nm (95% CI: -0.39, -0.09); (b) standardized relative to body weight at 240°/s, -0.11 Nm (95% CI: -0.17, -0.05); (c) standardized relative to body mass index at 60°/s, -0.84 Nm (95% CI: -1.23, -0.44); (d) standardized relative to body mass index at 240°/s, -0.32 Nm (95% CI: -0.52, -0.12); (e) nonstandardized in a concentric mode at 60°/s, -17.54 Nm (95% CI: -25.53, -9.54); (f) nonstandardized in a concentric mode at 240°/s, -7.72 Nm (95% CI: -12.67, -2.77). CONCLUSION: Weaker knee extension strength, expressed by peak torque, appears to be a risk factor for PFPS, based on meta-analyses of pooled results from multiple studies. Because several other risk factors for PFPS were described only in single studies, these additional risk factors, as well as those with conflicting evidence, need to be confirmed in future studies. LEVEL OF EVIDENCE: Prognosis, level 1a-.