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Causes. The shoulder joint is the most frequently dislocated joint of the body. Because it moves in several directions, your shoulder can dislocate forward, backward or downward, completely or partially, though most dislocations occur through the front of the shoulder. dislocated shoulder may be caused by: 1  Sports injuries. 2  Shoulder dislocation is a common injury in contact sports, such as football and hockey, and in sports that may involve falls, such as downhill skiing, gymnastics and volleyball. 3  Trauma not related to sports.
Shoulder osteoarthritis, also known as degenerative joint disease of the shoulder, is a gradual, progressive, mechanical, and biochemical breakdown of the articular cartilage and other joint tissues, including bone and joint capsule.steoarthritis of the shoulder is a gradual wearing of the articular cartilage that leads to pain and stiffness. As the joint surface degenerates, the subchondral bone remodels, losing its sphericity and congruity. The joint capsule also becomes thickened, leading to further loss of shoulder rotation.