I. Swelling of the knee joint. II. Synovitis with joint fluid exudation. III. Hematoma of the joint. IV. Septic arthritis. V. Lesions of the knee extension device. VI. Ligamentous lesions of the knee joint. Meniscal lesions. Patellar cartilage chondromalacia. Clinical features: chronic localized pain in the front of the knee joint, aggravated by sitting or going up and down stairs, mostly seen in women aged 15-35 years, the pathology is currently unclear, softening and fibrosis of the patellofemoral articular surface, followed by the development of osteoarthritis. When conservative treatment is not effective, patellectomy is feasible.