Effects of lower limb strengthening training on lower limb biomechanical characteristics and knee pain in patients with patellofemoral pain: a systematic review and meta-analysis

The objective of this study was to conduct a comprehensive comparison of the effects of hip and knee strengthening training in patients with patellofemoral pain (PFP). A meta-analysis was conducted to investigate the effects of these two types of strengthening training on patients' lower limb biomechanics, knee pain and function. The aim was to evaluate the effectiveness of the two training modalities and provide evidence-based recommendations for the rehabilitation of patients with PFP. A total of 12 studies were identified through a search of the Web of Science, EBSCO, and PubMed databases. The selected studies comprised nine randomized controlled trials (RCTs), one comparative controlled trial (CCTs) and two cohort studies (CSs), with a total of 1,066 patients. The quality of the included studies was evaluated via the PEDro scale, and a meta-analysis was conducted via Stata18 software. The results show that both types of strengthening training positively impact pain reduction and improved knee function in PFP patients. Moderate evidence from meta-analyses indicated that hip strengthening training (SMD = -1.740, 95%; CI -2.212 to -1.267, P < 0.001) was more effective than knee strengthening training (SMD = -1.302, 95%; CI -1.75 to -0.86, P < 0.001) in reducing pain (VAS). Similarly, Strong evidence suggests that hip strengthening training (SMD = 1.205, 95%; CI 0.968 to 1.443, P < 0.001) was significantly more effective than knee strengthening training (SMD = 1.023, 95%; CI 0.722 to 1.325, P < 0.001) in improving knee function (AKPS). Additionally, moderate evidence suggests that hip strengthening training significantly increased hip abductor strength (SMD = 0.848, 95%; CI 0.508-1.187, P < 0.001) and external rotator strength (SMD = 0.780, 95%; CI 0.416-1.145, P < 0.001), while strong evidence suggests that knee strengthening training did not significantly enhance knee extensor strength (SMD = 0.212, 95%; CI -0.014 to 0.439, P = 0.066). Therefore, clinicians should use hip strengthening as one of the primary training interventions when treating patients with PFP.