Dislocated shoulder

As the body’s most mobile joint, your shoulder joint is vulnerable to dislocation. Your upper arm bone usually rests in a cup-shaped pocket in your shoulder blade. A dislocated shoulder is an injury in which that upper arm bone pops out of its pocket.

Bursitis

Your shoulder joint has many moving parts. Bones come together at their ends to create joints, for example. Made of hard material, the bones of a joint would grind against each other as they move. The joints of your shoulder contain small fluid-filled sacs, known as bursae, to reduce friction between the moving joints of your shoulder.

Bursitis is a painful shoulder condition that develops as the result of inflammation or irritation of a bursa in your shoulder.

Frozen shoulder

Frozen shoulder causes stiffness and pain in your shoulder joint. The symptoms typically begin gradually, worsen over time, and then get better. Pain may worsen at night. During the first stage, also known as the freezing stage, you may notice limited range of motion in your shoulder and pain anytime you move the shoulder joint. During the second phase, known as the frozen stage, you will feel less pain but more stiffness in your shoulder joint. Your range of motion improves as you go through the final thawing stage.

Rotator Cuff Injury

A group of muscles and tendons, known collectively as the rotator cuff, keep the head of your upper arm bone securely in its socket in the shoulder. Injury to the rotator cuff might occur as the result of overuse or from a single injury. People who perform repeated motions over their heads, such as painters and basketball players, are at greater risk for rotator cuff injury.

Injury to the rotator cuff typically causes a dull ache in your shoulder. A rotator cuff injury might cause pain when you try to sleep on the affected side.

Strains and sprains

Sprains and strains share similar symptoms but affect different parts of your body. Strains occur when you stretch or tear a tendon, which is a cord of tissue that attaches the ends of your muscles to your bones. A sprain is an injury that involves ligaments, which are bands of tissue that connects the ends of two bones to form a joint.

Tendinitis

Tendinitis involves inflammation of a tendon to cause shoulder pain. Pain from tendinitis is usually a dull ache where the muscle meets the bone. The shoulder pain associated with tendinitis is usually more severe when you move the affected shoulder.