Children and adolescents Patellar subluxation Tibial apophysitis (Osgood-Schlatter lesion) Jumper's knee (patellar tendonitis) Referred pain: slipped capital femoral epiphysis, others Osteochondritis dissecans

Adults Patellofemoral pain syndrome (chondromalacia patellae) Medial plica syndrome Pes anserine bursitis Trauma: ligamentous sprains (anterior cruciate, medial collateral, lateral collateral), meniscal tear Inflammatory arthropathy: rheumatoid arthritis, Reiter's syndrome Septic arthritis

Older adults Osteoarthritis Crystal-induced inflammatory arthropathy: gout, pseudogout Popliteal cyst (Baker's cyst)