Biceps Femoris–Focused Eccentric Exercise Versus Standard Physiotherapy on Dynamic Knee Stability and Pain in Patients with Chronic Knee Pain: A Randomized Controlled Trial

Abstract

Background: A common musculoskeletal issue that can affect dynamic knee stability, balance functional performance and quality of life is chronic knee pain. Exercise therapy is a first-line treatment, but it’s unclear if Biceps Femoris-focused eccentric exercise has any additional benefits. Objective: To compare the effects of Biceps Femoris–focused eccentric exercise and regular physiotherapy on dynamic knee stability and pain in patients with chronic knee pain. Methods: This was a parallel group, single-blinded, randomized controlled trial conducted in the outpatient physiotherapy department of JPMC, BAWS Health Facility, Karachi, Pakistan, from 01 March 2026 to 31 August 2026. A total of 160 participants with chronic knee pain were randomly assigned to either the Biceps Femoris–focused eccentric exercise group (n = 80) or the standard physiotherapy exercise group (n = 80). For 6 weeks, both groups underwent 3 sessions of supervised exercise therapy three times per week for six weeks (18 sessions total). Progressive eccentric hamstring exercises emphasizing eccentric knee flexion, external tibial rotation and single-leg control were performed by the Biceps Femoris-focused eccentric exercise group. These exercises included Romanian deadlifts, lateral step-downs with external rotation cueing, prone knee curls with external tibial rotation, side-lying hip extension with knee flexed 30-45°, standing hip hinges with band resistance, single-leg squats to a box. Straight leg raises, mini-squats (0–45°), step-ups, terminal knee extension with band, static hamstring and calf stretches, and single-leg stance balance training were among the traditional knee rehabilitation exercises performed by the standard physiotherapy group. A total of 149 participants finished the study and were included in the final analysis (74 in the Biceps Femoris–focused eccentric exercise group and 75 in the standard physiotherapy group). The primary outcomes were dynamic knee stability which was assessed using the Star Excursion Balance Test, and pain intensity was assessed by using the Numerical Pain Rating Scale. Secondary outcomes were functional performance, knee-related disability, and adverse events. Data were analyzed using SPSS version 26.0, with statistical significance set at p < 0.05. Results: Dynamic knee stability, pain, functional performance and knee related disability all improved in both groups after six weeks. But compared to the standard physiotherapy group, the Biceps Femoris-focused eccentric exercise group significantly improved dynamic knee stability (mean change: 8.4 ± 3.1 vs. 3.6 ± 2.7; mean difference: 4.8; 95% CI: 3.9 to 5.7; p < 0.001). Additionally, the eccentric exercise group experienced a significantly higher reduction in pain (mean change: 3.3 ± 1.2 vs. 2.1 ± 1.3; mean difference: 1.2; 95% CI: 0.8 to 1.6; p < 0.001). Functional performance and knee related disability improved more in eccentric exercise group. The most frequent adverse event was mild muscle soreness; no significant adverse events were noted. Conclusion: For patients with chronic knee pain, Biceps Femoris-focused eccentric exercise was more beneficial than conventional physiotherapy in terms of enhancing dynamic knee stability and lowering pain. It might be suggested as a practical and safe supplement to conventional physiotherapy rehabilitation.