The shoulder is the most mobile joint in the human body. The joint includes four tendons. The purpose of a tendon is to hold muscle to bone. Together, these four "rotator cuff" tendons stabilize the upper arm bone to the shoulder socket and allow a wide range of motion in the shoulder.

Any swelling, inflammation, tearing, or bony changes around these tendons causes pain when a person tries to move the arm above the head, behind the back, or straight out in front.

The tendons pass underneath a rigid bony arch in the shoulder. The most common cause of shoulder pain is when the tendons become trapped under this arch. The compressed tendons become inflamed or damaged, a condition called rotator cuff tendinitis. This can occur from general wear and tear as you get older, an activity that requires constant shoulder use like baseball pitching, or an injury.

Shoulder pain can also be due to:

• Arthritis in the joints about the shoulder (gradual narrowing of the joints and loss of protective cartilage).
• Bursitis (inflammation of a fluid-filled sac, or bursa, that lies between tendon and skin or between tendon and bone). Normally a bursa protects the joint and helps make movement more fluid.
• Fractures of the shoulder bones.
• Frozen shoulder syndrome occurs when you don't move your shoulder because of pain or injury. The muscles or connective structures stiffen up inside the shoulder and make any motion painful and difficult.
• Inflammation of nearby tendons, such as those connected to the bicep muscles of your arms, from overuse or injury.
• Dislocation of your shoulder, which is when the ball-shaped head of your arm comes out of the socket.

When you first feel shoulder pain, apply ice for up to 15 minutes, then leave it off for 15 minutes. Repeat this cycle for several hours. Wrap the ice in a cloth, DO NOT apply ice directly to the skin. Then, continue to ice 3 to 4 times a day for 2 to 3 days.

Rest the shoulder from strenuous activity for the next few days. When the pain and swelling have subsided, gradually begin to strengthen the shoulder muscles. Perform light weight lifting, using a full range of motion. Consider seeing a physical therapist for help doing this safely.

Ibuprofen or acetaminophen (Tylenol) may help reduce inflammation and pain.