Hip muscle strength and endurance in females with patellofemoral pain: a systematic review with meta-analysis

PURPOSE/BACKGROUND: Patellofemoral pain (PFP) is a common knee conditions experienced by adolescents and young adults, seen particularly in women. Clinicians and researchers need to understand how proximal, local, or distal factors may influence the development of PFP and affect individuals once they have developed PFP. Proximal factors are the focus of recent studies and the purpose of this systematic review was to determine if females with PFP have hip muscle strength or endurance deficits when compared to their unaffected leg and to comparison groups. METHODS: A systematic review was conducted to identify relevant studies in the databases PubMed, PEDro, ScienceDirect and EBSCOhost up to June 2013. Data including study design, participants demographic data, and assessments of hip muscle strength or endurance were extracted from individual trials. The mean differences of hip muscles strength or endurance between females with PFP and healthy controls or unaffected side were extracted or calculated from individual trials and, when possible, a meta-analysis was performed. RESULTS: Ten cross-sectional studies were included in this review. Concerning isometric strength, pooled data reported deficit in hip abduction, extension, external rotation and flexion but no deficit in adduction and internal rotation when compared with healthy controls. When compared with the unaffected side, deficit in hip abduction was reported in two studies and deficit in extension and external rotation in one study. Studies with isokinetic strength evaluation reported deficit in abduction but contradictory results for extensors and rotators in females with PFPS. Finally, one study reported hip endurance deficit in extension and one found no significant differences in hip endurance compared to control subjects. CONCLUSION: The results of this systematic review confirm that females with PFPS have deficit in hip muscle strength compared with healthy controls and the unaffected side but are contradictory concerning endurance. LEVEL OF EVIDENCE: 2a