The shoulder is made up of three bones: the shoulder blade (scapula), the upper arm bone (humerus), and the collarbone (clavicle). The humerus fits into the scapula like a ball and socket. The shoulder can turn in many directions and is therefore also easy to dislocate. The rotator cuff, made of muscles and tendons, attaches the upper arm to the shoulder blade and helps to lift and rotate the arm.
Between the rotator cuff and the bone is a lubricating sac that protects the tendons and allows them to glide freely.
Pain in the shoulder can develop due to arthritis, inflammation, trauma, tears, dislocations, and fractures.
Inflammation in the shoulder mostly occurs in the tendons. Bursitis is one type of inflammation which affects the Bursae, small fluid-filled sacs that reduce friction between bones and tissues. When the shoulder is used excessively, the bursa can become inflamed, leading to swelling and pain, specifically with overhead activities.
Symptoms of bursitis are very similar to symptoms of tendinitis (also spelled tendonitis). Tendinitis is an inflammation of a tendon, usually caused by wear and tear of the tendon.
Rotator Cuff Injuries
The rotator cuff muscles provide us the ability to reach overhead; therefore athletes who participate in sports that require a lot of overhead motions are more susceptible to such injuries. Repetitive lifting or a minor injury can also cause pain associated with the rotator cuff.
Also common are tears to the tendons of the rotator cuff, resulting in pain that radiates down the side of the arm.
Instability and dislocations
Because the shoulder is the most mobile joint in our bodies, it is very easy to dislocate. A dislocation occurs when the top of your arm bone is either partly out of the shoulder socket (partial dislocation), or when it is completely out of the socket (complete dislocation). The shoulder joint can dislocate toward the front, the back, and downward. The most common form of a dislocation is forward, usually caused by a forceful twist, a fall, or a direct blow to the shoulder.
Once a dislocation has taken place, the shoulder remains vulnerable, which might lead to continued dislocations. When dislocations occur repeatedly, it is called chronic shoulder instability. Another term used to describe a shoulder dislocation is a “separated shoulder.” However, the joint involved is not the shoulder joint but the acromioclavicular joint. A person suffering from a shoulder separation suffers from pain over the top of the affected shoulder sometimes accompanied by a bump.
Shoulder fractures are mostly caused by a fall or a direct blow to the shoulder area. Common shoulder fractures involve the clavicle, scapula, and humerus. These fractures result in severe pain and bruising.