Biomechanics of Shoulder Injuries

Shoulder injuries have a variety of causes. The joints in the shoulder and the muscles that help control movement can become unaligned, torn or overextended. Understanding the biomechanics of how the shoulder works can help patients understand their conditions.

Parts of the Shoulder

• The three joints in the human shoulder are the glenohumeral joint (a ball-and-socket joint), the sternoclavicular joint and the acromioclavicular joint. The muscles and tendons in the shoulder that hold the joints together are known collectively as the rotator cuff.

Types of Injuries

• Biomechanical shoulder injuries include tears, strains, impingement and bursitis. Impingement occurs when the humerus rubs against the acromion during movement. This is generally caused by bursitis, an inflammation of a sac (the bursa sac) that helps prevent bone-on-bone rubbing. Tears and strains can happen to various parts of the shoulder muscles, but the most common, especially among athletes, is a rotator cuff tear. This occurs when the rotator cuff muscles are overworked or overstretched during physical activity.

Treatment

• Treatment of shoulder injuries varies, depending on the type and severity of injuries. Ice and heat therapies are common conservative treatments. Doctors may also administer steroid shots to combat impingement or bursitis; physical therapy is also an option. Shoulder injuries sometimes require surgery.