Effectiveness of Hip Muscle Strengthening Compared with Knee Strengthening or No Intervention in Individuals with Patellofemoral Pain Syndrome: A Systematic Review.

Background: Patellofemoral pain syndrome (PFPS) is a common musculoskeletal condition in physically active individuals. Although quadriceps strengthening has traditionally been the cornerstone of conservative management, hip-strengthening exercises have gained increasing attention because of their potential to improve lower-limb biomechanics. However, the optimal exercise prescription for PFPS remains uncertain. Objective: To evaluate the effectiveness of isolated or combined hip muscle strengthening compared with knee strengthening or no intervention on pain, physical function, and muscle strength in individuals with PFPS. Methods: A systematic review was conducted in accordance with PRISMA guidelines and registered in PROSPERO (CRD420261342475). PubMed, PEDro, the Cochrane Library, CINAHL, and Web of Science were searched from inception to 31 December 2025. Randomised controlled trials comparing hip-strengthening interventions with knee strengthening or no intervention were included. Methodological quality, risk of bias, and certainty of evidence were assessed using the PEDro scale, the Cochrane RoB 2 tool, and the GRADE approach, respectively. Results: Fifteen randomised controlled trials involving 1002 participants were included. Exercise therapy consistently improved pain, physical function and muscle strength. Both hip- and knee-strengthening programmes were superior to no intervention. Programmes incorporating hip strengthening may provide greater reductions in pain and larger improvements in proximal muscle strength than knee-focused programmes, whereas functional outcomes were generally comparable. Combined hip- and knee-strengthening programmes appeared to provide the most consistent overall clinical benefits. The overall certainty of the evidence was moderate for all outcomes. Conclusions: Current evidence supports exercise-based rehabilitation for PFPS, while evidence remains insufficient to determine whether any specific strengthening strategy provides a clear overall advantage. Further high-quality randomised controlled trials are needed to determine the optimal exercise prescription.