This randomized controlled trial aims to investigate the effects of isokinetic training combined with blood flow restriction (BFR) in individuals with patellofemoral pain syndrome (PFPS).

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.