of man, a spherical joint formed by the union of the head of the humeral bone with the joint surface of the shoulder blade.
A variety of movements in the shoulder joint are possible, including abduction, adduction, flexion, and extension. The joint is surrounded by an elastic capsule and strengthened by a ligament and a thick layer of muscles surrounding the joint. It is supplied with blood through the anterior and posterior humeral arteries and innervated by the axillary nerve and branches of the long thoracic, radial, and subscapular nerves.
Among the congenital diseases of the shoulder joint are developmental anomalies and habitual dislocations. The acquired diseases include arthritis, rheumatoid arthritis, and periarthritis. Mechanical injuries to the shoulder joint include dislocation of the head of the humerus, fractures of the neck and head of the humerus, and tears and strains of the surrounding ligaments, tendons, and muscles.