Low-Intensity Blood Flow-Restricted Multi-Joint Exercise Improves Muscle Function in Patients With Patellofemoral Pain Syndrome: A Randomized Trial

BACKGROUND Patellofemoral pain syndrome (PFPS) limits physical activity and quality of life, especially during weight-bearing tasks. Although high-load resistance exercises are recommended for rehabilitation, they may worsen symptoms in pain-sensitive individuals. Low-intensity blood flow restriction (BFR) training has emerged as a potential alternative. However, its effects on functional performance and mechanical properties remain unclear. MATERIAL AND METHODS In this assessor-blinded, randomized controlled trial, 41 individuals with PFPS were randomly assigned to either the experimental group (EG, n=20) or the control group (CG, n=19). The EG performed multi-joint resistance exercises combined with BFR, while the CG performed the same program without BFR. Both groups completed the same multi-joint resistance exercise program twice weekly for 6 weeks. Outcome measures included pressure pain threshold (PPT), muscle mechanical properties such as tone and stiffness in the vastus medialis and vastus lateralis, isometric knee extensor strength, and balance ability. Balance was evaluated using the Y-Balance Test and the stair-descending task. RESULTS The EG showed significantly greater improvements in knee strength, PPT, and balance (P<0.05). Notably, significant increases in muscle tone were observed in the vastus medialis and lateralis muscles, as well as muscle stiffness in the vastus medialis and semitendinosus muscles. CONCLUSIONS Low-intensity BFR multi-joint resistance exercise may be an effective intervention for improving physical function, pain, and mechanical properties in patients with PFPS.