Arthropathy associated with severe hypothyroidism
Myxedematous arthropathy typically affects the knee and hand joints. The patient presents with swelling and stiffness. Synovial thickening, ligamentous laxity, and effusions with a characteristic slow fluid wave (bulge sign) are common. The synovial fluid is noninflammatory, with an increased viscosity due to high hyaluronic acid levels resulting in a string sign of 1 to 2 feet instead of the normal 1 to 2 inches. Radiographs are typically normal.
Osteonecrosis can also occur (controversial). In adults, it typically involves the hip or tibial plateau. In children, abnormal epiphyseal ossification may occur which can be confused with epiphyseal dysplasia or juvenile avascular necrosis (Legg–Calvé–Perthes disease) of the hip.
