Isokinetic Training With Blood Flow Restriction for Patellofemoral Pain Syndrome

Inclusion Criteria: * Participants aged 18 to 40 years. * Clinical diagnosis of patellofemoral pain syndrome (PFPS). * Presence of anterior or retropatellar knee pain for at least 3 months. * Pain provoked by at least two activities that increase patellofemoral joint load, including squatting, stair climbing, running, jumping, prolonged sitting, or kneeling. * Average knee pain intensity of ≥3 on a 10-point visual analog scale (VAS) during aggravating activities. * Ability to participate in exercise training and attend scheduled intervention sessions. * Willingness to provide written informed consent. Exclusion Criteria: * History of knee surgery or significant trauma to the lower extremity within the previous 12 months. * Clinical evidence of other knee disorders, including ligament injury, meniscal injury, patellar instability, osteoarthritis, or tendinopathy. * Presence of neurological, cardiovascular, or systemic musculoskeletal disorders that may affect lower limb function or exercise participation. * Current participation in other structured lower extremity rehabilitation or strength training programs. * Contraindications to blood flow restriction training, including uncontrolled hypertension, vascular disease, thromboembolic disorders, or clotting abnormalities. * Use of pain-relieving injections or surgical interventions for knee pain within the previous 6 months. * Pregnancy. * Inability to complete the assessment or intervention procedures.