FOOT INVOLVEMENT

Joint involvement in the foot resembles that in the hand, except for deformities that are determined chiefly by the foot’s weight-bearing function (see Plate 5-4). The toes usually become hyperextended, or cocked up, at the metatarsophalangeal joints and flexed at the proximal interphalangeal articulations (hammertoes). The joint capsules, fasciae, and tendons become stretched and weakened, and the metatarsal and longitudinal arches flatten. Standing and walking exert great pressure on the osteoporotic metatarsal heads, causing severe erosion of the metatarsals. Frequently, plantar callosities develop under the metatarsal heads. Hallux valgus with bunion formation is also common. Cartilage thinning of the intertarsal joints is usually so severe that the tarsus becomes quite rigid, adding strain to the inflamed ankle joint. These structural changes make walking both difficult and painful.

KNEE, SHOULDER, AND HIP INVOLVEMENT

Inflammation of the large joints of the limbs causes a boggy and diffuse swelling of the soft tissues of the joints. In the elbows and knees, this swelling is easily observed on physical examination (see Plate 5-5). Involvement of the hip and shoulder joints, on the other hand, cannot be detected by inspection and palpation because the hips and, to a lesser degree, the shoulders lie deep beneath the skin and are well covered by fleshy muscles. Examination for range of motion elicits pain and restricted movement if the joints are inflamed. In these large, well-covered joints, radiographs are required to evaluate the damage to the articular cartilage.