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 your joint. Your cartilage becomes cracked and pitted, and your socket may wear down. Eventually, your bone is exposed and may develop growths called spurs. Without a cushion of cartilage, your joint becomes stiff and painful. It 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. Your synovium (the membrane that lines your joints) thickens. It then forms a tissue growth (pannus) that clings to your cartilage and releases chemicals that destroy it. Your joint may become red, swollen, and warm. Pain may radiate into your neck and arm. Over time, your joint may get stiff and your muscles may weaken from disuse. Your bone may also be destroyed.
A fracture can occur when you fall on an outstretched hand or elbow. The ball and/or tuberosities can break off, leaving your 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 your bone to be cut off. As the bone dies, it collapses. Your 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 your acromion, your joint becomes painful, stiff, and weak. Surgery can relieve the pain, but you may never regain flexibility and strength.