Arthroscopy allows diagnosis and treatment of conditions affecting the synovium as villonodular synovitis, the synovial chondromatosis, rheumatoid arthritis and crystal deposition arthritis. As a diagnostic tool, arthroscopy allows biopsy with great precision, as it allow the inspection and tissue biopsy of the most inflammatory tissue. Therapeutically, arthroscopic synovectomy and removal of chondral and osteochondral free body can be done.