Arthritis, injury, bone disease, and torn muscles and tendons can cause pain, stiffness, and sometimes swelling in your shoulder. Then even simple movements become painful and difficult.
Osteoarthritis is a wearing away of the joint. The cartilage becomes cracked and pitted, and the socket may wear down. Eventually, the bone is exposed and may develop growths called spurs. Without a cushion of cartilage, the joint becomes stiff and painful and may feel as if it's grinding or slipping out of place when you move your arm.
Inflammatory (Rheumatoid) Arthritis
Inflammatory arthritis is a chronic joint disease. The synovium thickens and forms a tissue growth (pannus) that clings to the cartilage and releases chemicals that destroy it. The joint may become red, swollen, and warm, and pain may radiate into the neck and arm. Over time, the joint may get stiff and the muscles may weaken from disuse. The bone may also be destroyed.
A fracture can occur when you fall on an outstretched hand or elbow. The ball and tuberosities break off, leaving the arm bone in pieces. A fractured shoulder is painful and may be black and blue and look deformed.
A number of conditions, including long-term use of steroids or alcohol, can cause the blood supply to the bone to be cut off. As the bone dies, it collapses. The shoulder becomes painful and movement is limited.
Rotator Cuff Tear
A chronic rotator cuff tear may lead to severe arthritis. As the ball rides up against the acromion, the joint becomes painful, stiff, and weak. Surgery can relieve the pain, but flexibility and strength may never be regained.