A Comparative Analysis of Lower Limb Muscle Activation and Co-Contraction Patterns During Gait in Individuals With Patellofemoral Pain Syndrome
Abstract
Background. Patellofemoral pain syndrome (PFPS) is a prevalent musculoskeletal condition that disrupts functional activities like walking and stair climbing due to anterior knee pain. While muscle weakness has traditionally been emphasised, growing evidence suggests that impaired neuromuscular coordination may also play a critical role in PFPS-related gait dysfunction.
Aim. This study aimed to compare lower-limb muscle activation patterns and co-contraction behaviour during gait between individuals with PFPS and healthy controls, focusing on both timing and intensity of activation across key knee and ankle muscle groups.
Methods. Fifteen PFPS patients and fifteen age- and activity-matched healthy controls walked at a self-selected pace while surface electromyography (EMG) data were recorded from eight lower-extremity muscles. EMG signals were processed to extract normalised peak activation timing, magnitude, and co-contraction indices (CCI) for knee and ankle joints. Between-group comparisons were conducted using independent t-tests and Pearson correlation analyses.
Results. The PFPS group exhibited significantly earlier (VL: 13% vs. 100%; RF: 4% vs. 98% of stance, both p < 0.05) and greater peak activation (VL: 0.202 vs. 0.112; RF: 0.109 vs. 0.062, both p < 0.05) in the quadriceps. They also showed delayed hamstring (ST: 100% vs. 3% of stance, p < 0.05) activation and increased medial gastrocnemius amplitude (GM: 0.282 vs. 0.161, p < 0.05). Despite these timing shifts, average CCI values did not differ significantly between groups. However, flexor–extensor activation synchrony was notably higher in PFPS (r ≈ 0.82) compared with controls (r ≈ 0.39).
Conclusions. Individuals with PFPS demonstrate altered neuromuscular control during gait, including phase-shifted activation of knee muscles and modified ankle muscle recruitment. These changes may elevate joint stress and contribute to persistent pain. Rehabilitation programmes should emphasise not only muscle strengthening but also retraining of activation timing and coordination to promote more efficient and pain-free gait patterns.
Keywords: patellofemoral pain syndrome; gait; electromyography; muscle activation; co-contraction
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