Patellofemoral Pain Syndrome

Patellofemoral pain syndrome is anterior knee pain arising from the patellofemoral joint without structural intra articular pathology. It is the most common cause of knee pain in active people, with a prevalence of about 22% in adults and 28% in adolescents, and a female to male ratio of about 2 to 1.

It results from load exceeding the joint's tolerance. Contributing factors are hip abductor and external rotator weakness, quadriceps weakness, patellar maltracking, foot pronation, tight hamstrings and iliotibial band, and sudden increases in training. Up to 40% still have pain at 5 years, and it is a risk for later patellofemoral osteoarthritis in some.

• Diffuse retropatellar or peripatellar pain, worse on stairs, squatting, running, and prolonged sitting (the theatre sign)
• Crepitus without effusion
• Pain on patellar compression, a positive single leg squat test, tenderness of the patellar facets, and weak hip abduction
• Red flags: effusion, locking, giving way, trauma, night pain, fever, and an adolescent with hip or thigh pain (slipped capital femoral epiphysis)

• Clinical diagnosis by history and examination (pain on squatting and on step down).
• Radiographs (including skyline view) only when pain is atypical or persistent.
• MRI only for red flags such as effusion, mechanical symptoms or trauma.

Differentials: patellar tendinopathy, Osgood-Schlatter disease, Sinding-Larsen-Johansson syndrome, plica syndrome, fat pad impingement, bipartite patella, meniscal tear, patellar instability, referred pain from the hip.

• Exercise therapy as first line for 6 to 12 weeks: hip abduction and external rotation strengthening, quadriceps strengthening (closed chain with a knee flexion limit of 45 degrees initially), and calf and hamstring stretching.
• Load management: reduce running volume and hills, avoid deep squats and prolonged flexion in the early phase, and increase training by under 10% weekly.
• Taping (medial glide) and foot orthoses for 4 to 6 weeks as adjuncts for pronated feet.
• Paracetamol 1 g orally every 6 hours or ibuprofen 400 mg three times daily with food for up to 2 weeks (children 10 mg/kg/dose).
• Avoid intra articular corticosteroid injection and arthroscopic lateral release. Operative treatment is rare and reserved for proven maltracking after over 6 months of failed rehabilitation.

Follow up at 6 and 12 weeks. Counsel on weight control, footwear and activity pacing. Recurrence is common without continued hip and quadriceps strength work.