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Patellofemoral pain affects a large proportion of the population, from adolescents to older adults, and carries a substantial personal and societal burden. An international group of scientists and clinicians meets biennially at the International Patellofemoral Research Retreat to share research findings related to patellofemoral pain conditions and develop consensus statements using best practice methods. This consensus statement, from the 5th International Patellofemoral Research Retreat held in Australia in July 2017, focuses on exercise therapy and physical interventions (eg, orthoses, taping and manual therapy) for patellofemoral pain. Literature searches were conducted to identify new systematic reviews and randomised controlled trials (RCTs) published since the 2016 Consensus Statement. The methodological quality of included systematic reviews and RCTs was graded using AMSTAR and PEDro, respectively. Evidence-based statements were developed from included papers and presented to a panel of 41 patellofemoral pain experts for consensus discussion and voting. Recommendations from the expert panel support the use of exercise therapy (especially the combination of hip-focused and knee-focused exercises), combined interventions and foot orthoses to improve pain and/or function in people with patellofemoral pain. The use of patellofemoral, knee or lumbar mobilisations in isolation, or electrophysical agents, is not recommended. There is uncertainty regarding the use of patellar taping/bracing, acupuncture/dry needling, manual soft tissue techniques, blood flow restriction training and gait retraining in patients with patellofemoral pain. In 2017, we launched the International Patellofemoral Research Network (www.ipfrn.org) to consolidate and grow our patellofemoral research community, facilitate collaboration and disseminate patellofemoral pain knowledge to clinicians and the general public. The 6th International Patellofemoral Research Retreat will be held in Milwaukee, Wisconsin, USA, in October 2019.

BackgroundAbnormal gait after anterior cruciate ligament reconstruction (ACLR) may contribute to development and/or progression of knee osteoarthritis.ObjectiveTo conduct a systematic review and meta-analysis of knee kinematics and joint moments during walking after ACLR.MethodsWe searched seven electronic databases and reference lists of relevant papers, for cross-sectional, human-based observational studies comparing knee joint kinematics and moments during level walking in individuals with ACLR, with the uninjured contralateral knee or healthy individuals as a control. Two independent reviewers appraised methodological quality (modified Downs and Black scale). Where possible, data were pooled by time post-ACLR (RevMan), otherwise narrative synthesis was undertaken.ResultsThirty-four studies were included. Meta-analysis revealed significant sagittal plane deficits in ACLR knees. We found greater knee flexion angles (standardised mean difference: 1.06; 95% CI 0.39 to 1.74) and joint moments (1.61; 0.87 to 2.35) <6 months post-ACLR, compared to healthy controls. However, lower peak knee flexion angles were identified 1–3 years (−2.21; −3.16 to −1.26) and ≥3 years post-ACLR (−1.38, −2.14 to −0.62), and lower knee flexion moment 6–12 months post-ACLR (−0.76; −1.40 to −0.12). Pooled data provided strong evidence of no difference in peak knee adduction moment >3 years after ACLR (vs healthy controls) (0.09; −0.63 to 0.81). No transverse plane conclusions could be drawn.ConclusionsSagittal plane biomechanics, rather than the knee adduction moment, appear to be more relevant post-ACLR. Better understanding of sagittal plane biomechanics is necessary for optimal post-operative recovery, and to potentially prevent early onset and progression of knee OA after ACLR.Trial registration numberPROSPERO systematic review protocol registration number CRD4201400882 2.

BackgroundPatellofemoral osteoarthritis (PF OA) is more prevalent than previously thought and contributes to patient’s suffering from knee OA. Synthesis of prevalence data can provide estimates of the burden of PF OA.ObjectiveThis study aims to conduct a systematic review and meta-analysis on the prevalence of PF OA and structural damage based on radiography and MRI studies in different populations.MethodsWe searched six electronic databases and reference lists of relevant cross-sectional and observational studies reporting the prevalence of PF OA. Two independent reviewers appraised methodological quality. Where possible, data were pooled using the following categories: radiography and MRI studies.ResultsEighty-five studies that reported the prevalence of patellofemoral OA and structural damage were included in this systematic review. Meta-analysis revealed a high prevalence of radiographic PF OA in knee pain or symptomatic knee OA (43%), radiographic knee OA or at risk of developing OA (48%) and radiographic and symptomatic knee OA (57%) cohorts. The MRI-defined structural PF damage in knee pain or symptomatic population was 32% and 52% based on bone marrow lesion and cartilage defect, respectively.ConclusionOne half of people with knee pain or radiographic OA have patellofemoral involvement. Prevalence of MRI findings was high in symptomatic and asymptomatic population. These pooled data and the variability found can provide evidence for future research addressing risk factors and treatments for PF OA.Trial registration numberPROSPERO systematic review protocol (CRD42016035649).

BackgroundKnee MRI is increasingly used to inform clinical management. Features associated with osteoarthritis are often present in asymptomatic uninjured knees; however, the estimated prevalence varies substantially between studies. We performed a systematic review with meta-analysis to provide summary estimates of the prevalence of MRI features of osteoarthritis in asymptomatic uninjured knees.MethodsWe searched six electronic databases for studies reporting MRI osteoarthritis feature prevalence (ie, cartilage defects, meniscal tears, bone marrow lesions and osteophytes) in asymptomatic uninjured knees. Summary estimates were calculated using random-effects meta-analysis (and stratified by mean age: <40 vs ≥40 years). Meta-regression explored heterogeneity.ResultsWe included 63 studies (5397 knees of 4751 adults). The overall pooled prevalence of cartilage defects was 24% (95% CI 15% to 34%) and meniscal tears was 10% (7% to 13%), with significantly higher prevalence with age: cartilage defect <40 years 11% (6%to 17%) and ≥40 years 43% (29% to 57%); meniscal tear <40 years 4% (2% to 7%) and ≥40 years 19% (13% to 26%). The overall pooled estimate of bone marrow lesions and osteophytes was 18% (12% to 24%) and 25% (14% to 38%), respectively, with prevalence of osteophytes (but not bone marrow lesions) increasing with age. Significant associations were found between prevalence estimates and MRI sequences used, physical activity, radiographic osteoarthritis and risk of bias.ConclusionsSummary estimates of MRI osteoarthritis feature prevalence among asymptomatic uninjured knees were 4%–14% in adults aged <40 years to 19%–43% in adults ≥40 years. These imaging findings should be interpreted in the context of clinical presentations and considered in clinical decision-making.

Background Running participation continues to increase. The ideal strike pattern during running is a controversial topic. Many coaches and therapists promote non-rearfoot strike (NRFS) running with a belief that it can treat and prevent injury, and improve running economy. Objective The aims of this review were to synthesise the evidence comparing NRFS with rearfoot strike (RFS) running patterns in relation to injury and running economy (primary aim), and biomechanics (secondary aim). Design Systematic review and meta-analysis. Consideration was given to within participant, between participant, retrospective, and prospective study designs. Data Sources MEDLINE, EMBASE, CINAHL, and SPORTDiscus. Results Fifty-three studies were included. Limited evidence indicated that NRFS running is retrospectively associated with lower reported rates of mild (standard mean difference (SMD), 95% CI 3.25, 2.37–4.12), moderate (3.65, 2.71–4.59) and severe (0.93, 0.32–1.55) repetitive stress injury. Studies prospectively comparing injury risk between strike patterns are lacking. Limited evidence indicated that running economy did not differ between habitual RFS and habitual NRFS runners at slow (10.8–11.0 km/h), moderate (12.6–13.5 km/h), and fast (14.0–15.0 km/h) speeds, and was reduced in the immediate term when an NRFS-running pattern was imposed on habitual RFS runners at slow (10.8 km/h; SMD = − 1.67, − 2.82 to − 0.52) and moderate (12.6 km/h; − 1.26, − 2.42 to − 0.10) speeds. Key biomechanical findings, consistently including both comparison between habitual strike patterns and following immediate transition from RFS to NRFS running, indicated that NRFS running was associated with lower average and peak vertical loading rate (limited-moderate evidence; SMDs = 0.72–2.15); lower knee flexion range of motion (moderate-strong evidence; SMDs = 0.76–0.88); reduced patellofemoral joint stress (limited evidence; SMDs = 0.63–0.68); and greater peak internal ankle plantar flexor moment (limited evidence; SMDs = 0.73–1.33). Conclusion The relationship between strike pattern and injury risk could not be determined, as current evidence is limited to retrospective findings. Considering the lack of evidence to support any improvements in running economy, combined with the associated shift in loading profile (i.e., greater ankle and plantarflexor loading) found in this review, changing strike pattern cannot be recommended for an uninjured RFS runner. PROSPERO Registration CRD42015024523.

Background Patellofemoral pain (PFP) is a prevalent knee condition with many proposed biomechanically orientated etiological factors and treatments. Objective We aimed to systematically review and synthesize the evidence for biomechanical variables (spatiotemporal, kinematic, kinetic) during walking and running in people with PFP compared with pain-free controls, and determine if biomechanical variables contribute to the development of PFP. Design Systematic review and meta-analysis. Data sources We searched Medline, CINAHL, SPORTDiscus, Embase, and Web of Science from inception to October 2021. Eligibility criteria for selecting studies All study designs (prospective, case–control [± interventional component, provided pre-intervention data were reported for both groups], cross-sectional) comparing spatiotemporal, kinematic, and/or kinetic variables during walking and/or running between people with and without PFP. Results We identified 55 studies involving 1300 people with PFP and 1393 pain-free controls. Overall pooled analysis identified that people with PFP had slower gait velocity [moderate evidence, standardized mean difference (SMD) − 0.50, 95% confidence interval (CI) − 0.72, − 0.27], lower cadence (limited evidence, SMD − 0.43, 95% CI − 0.74, − 0.12), and shorter stride length (limited evidence, SMD − 0.46, 95% CI − 0.80, − 0.12). People with PFP also had greater peak contralateral pelvic drop (moderate evidence, SMD − 0.46, 95% CI − 0.90, − 0.03), smaller peak knee flexion angles (moderate evidence, SMD − 0.30, 95% CI − 0.52, − 0.08), and smaller peak knee extension moments (limited evidence, SMD − 0.41, 95% CI − 0.75, − 0.07) compared with controls. Females with PFP had greater peak hip flexion (moderate evidence, SMD 0.83, 95% CI 0.30, 1.36) and rearfoot eversion (limited evidence, SMD 0.59, 95% CI 0.03, 1.14) angles compared to pain-free females. No significant between-group differences were identified for all other biomechanical variables. Data pooling was not possible for prospective studies. Conclusion A limited number of biomechanical differences exist when comparing people with and without PFP, mostly characterized by small-to-moderate effect sizes. People with PFP ambulate slower, with lower cadence and a shortened stride length, greater contralateral pelvic drop, and lower knee flexion angles and knee extension moments. It is unclear whether these features are present prior to PFP onset or occur as pain-compensatory movement strategies given the lack of prospective data. Trial Registration PROSPERO # CRD42019080241.

BackgroundPatellofemoral pain (PFP) occurs frequently, and may be related to patellofemoral osteoarthritis (PFOA). Obesity is associated with increased risk of knee OA. This systematic review involves a meta-regression and analysis to determine the relationship between body mass index (BMI) and PFP and PFOA, and to determine the link between BMI and interventional outcomes.MethodsWe searched seven electronic databases and reference lists of relevant papers and systematic reviews, for cross-sectional, prospective, human-based observational and interventional studies reporting BMI in individuals with PFP or PFOA compared to healthy controls. Two independent reviewers appraised methodological quality (epidemiological appraisal instrument). Where possible, data from prospective studies were pooled to conduct meta-regression and case–control, and intervention studies to conduct meta-analysis using the following categories: adolescents with PFP, adults with PFP and PFOA.Results52 studies were included. We found greater BMI in adults with PFP (standardised mean difference: 0.24, 95% CI 0.12 to 0.36) and PFOA (0.73, 0.46 to 0.99) compared to healthy controls, but not in adolescents with PFP (−0.19, −0.56 to 0.18). We also observed statistical trends (p<0.10) towards higher BMI being a predictor for development of PFP in adults (0.34, −0.04 to 0.71). No significant link between BMI and intervention outcomes in adults with PFP was identified.ConclusionsHigher BMI is present in PFP and PFOA, but not in adolescents with PFP.PROSPERO registration numberCRD42015024812.

ObjectiveTo explore clinical characteristics in individuals with patellofemoral osteoarthritis (PFOA) compared to individually-matched asymptomatic controls. We also explored associations between functional performance and patient-reported symptoms with patellofemoral alignment.MethodsWe assessed 15 individuals with PFOA and 15 individually-matched asymptomatic controls. In addition to physical examination and patient-reported questionnaires, we evaluated functional performance, lower extremity strength and range of motion, and patellar alignment (using MRI). We analysed group differences with Wilcoxon’s matched-pairs signed rank tests, and within-group associations with Spearman’s rank correlations.ResultsWe included 24 (80%) women with median (IQR) age of 56 (9) years and BMI of 22.8 (5.9) kg/m2. Individuals with PFOA reported lower quality of life (8/100 points lower EQ-5D-5L, p=0.02), and performed worse on two functional tests: repeated one-leg rises (median 16 fewer rises, p=0.04) and timed stair climb (1.2 s slower, p=0.03). There were no differences in strength tests performed or range of motion. Patellar proximal translation correlated with worse functional performance and worse patient-reported pain, function and self-efficacy, while lateral translation and lateral tilt correlated with worse knee-related quality of life (Spearman’s r ranging from 0.5 to 0.7).ConclusionFunctional performance was worse in individuals with PFOA, despite those individuals having no significant differences on lower extremity strength testing. Patellofemoral alignment was associated with worse functional performance as well as worse patient-reported outcomes, and it may represent one mechanism underpinning PFOA-related symptoms.

ObjectiveTo systematically review and synthesise patellofemoral joint reaction force (PFJRF) in healthy individuals and those with patellofemoral pain and osteoarthritis (OA), during everyday activities, therapeutic exercises and with physical interventions (eg, foot orthotics, footwear, taping, bracing).DesignA systematic review with meta-analysis.Data sourcesMedline, Embase, Scopus, CINAHL, SportDiscus and Cochrane Library databases were searched.Eligibility criteriaObservational and interventional studies reporting PFJRF during everyday activities, therapeutic exercises, and physical interventions.ResultsIn healthy individuals, the weighted average of mean (±SD) peak PFJRF for everyday activities were: walking 0.9±0.4 body weight (BW), stair ascent 3.2±0.7 BW, stair descent 2.8±0.5 BW and running 5.2±1.2 BW. In those with patellofemoral pain, peak PFJRF were: walking 0.8±0.2 BW, stair ascent 2.5±0.5 BW, stair descent 2.6±0.5 BW, running 4.1±0.9 BW. Only single studies reported peak PFJRF during everyday activities in individuals with patellofemoral OA/articular cartilage defects (walking 1.3±0.5 BW, stair ascent 1.6±0.4 BW, stair descent 1.0±0.5 BW). The PFJRF was reported for many different exercises and physical interventions; however, considerable variability precluded any pooled estimates.SummaryEveryday activities and exercises involving larger knee flexion (eg, squatting) expose the patellofemoral joint to higher PFJRF than those involving smaller knee flexion (eg, walking). There were no discernable differences in peak PFJRF during everyday activities between healthy individuals and those with patellofemoral pain/OA. The information on PFJRF may be used to select appropriate variations of exercises and physical interventions.

Background Foot and ankle characteristics are associated with patellofemoral pain (PFP) and may also relate to patellofemoral osteoarthritis (PFOA). A greater understanding of these characteristics and PFOA, could help to identify effective targeted treatments. Objectives To determine whether foot and ankle characteristics are associated with knee symptoms and function in individuals with PFOA. Methods For this cross-sectional study we measured weightbearing ankle dorsiflexion range of motion, foot posture (via the Foot Posture Index [FPI]), and midfoot mobility (via the Foot Measurement Platform), and obtained patient-reported outcomes for knee symptoms and function (100 mm visual analogue scales, Anterior Knee Pain Scale [AKPS], Knee injury and Osteoarthritis Outcome Score, repeated single step-ups and double-leg sit-to-stand to knee pain onset). Pearson’s r with significance set at p  < 0.05 was used to determine the association between foot and ankle charateristics, with knee symptoms and function, adjusting for age. Results 188 participants (126 [67%] women, mean [SD] age of 59.9 [7.1] years, BMI 29.3 [5.6] kg/m 2 ) with symptomatic PFOA were included in this study. Lower weightbearing ankle dorsiflexion range of motion had a small significant association with higher average knee pain (partial r = − 0.272, p  < 0.001) and maximum knee pain during stair ambulation (partial r = − 0.164, p  = 0.028), and lower scores on the AKPS (indicative of greater disability; partial r = 0.151, p  = 0.042). Higher FPI scores (indicating a more pronated foot posture) and greater midfoot mobility (foot mobility magnitude) were significantly associated with fewer repeated single step-ups (partial r = − 0.181, p  = 0.023 and partial r = − 0.197, p  = 0.009, respectively) and double-leg sit-to-stands (partial r = − 0.202, p  = 0.022 and partial r = − 0.169, p  = 0.045, respectively) to knee pain onset, although the magnitude of these relationships was small. The amount of variance in knee pain and disability explained by the foot and ankle characteristics was small (R 2 -squared 2 to 8%). Conclusions Lower weightbearing ankle dorsiflexion range of motion, a more pronated foot posture, and greater midfoot mobility demonstrated small associations with worse knee pain and greater disability in individuals with PFOA. Given the small magnitude of these relationships, it is unlikely that interventions aimed solely at addressing foot and ankle mobility will have substantial effects on knee symptoms and function in this population. Trial registration The RCT was prospectively registered on 15 March 2017 with the Australia and New Zealand Clinical Trials Registry ( ANZCTRN12617000385347 ).