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Shoulder pain is an extremely common complaint. Up to 26% of the population has it to some degree, and it ranks third—behind back pain and knee pain—in musculoskeletal conditions (those involving the bones, muscles, and related structures) that lead people to consult their doctor. About 1% of the population visits a doctor for shoulder pain each year, and while there are a number of possible issues that may be responsible, several similarities tend to be consistent throughout.

The causes of shoulder pain can generally be categorized into two groups: 1) traumatic (acute) injuries that immediately damage certain structures of the shoulder, and 2) overuse injuries, which occur gradually over time due to continuous strain on the shoulder. In both cases, those who are most likely to experience shoulder pain are individuals who regularly perform overhead movements. These types of movements are necessary in professions like painting and construction, and in sports like baseball, swimming, and tennis, making those who are involved in these activities vulnerable to all types of shoulder issues.

Any component of the shoulder can be damaged in an acute or overuse injury, but the majority of shoulder conditions—about 85%—involve the rotator cuff. The rotator cuff is an important group of four muscles that surround the bones of the shoulder. Each of these muscles spans from a different part of the shoulder blade (scapula) to the head of the upper arm bone (humerus) to form a “cuff” that controls and stabilizes the shoulder. A number of issues can affect the rotator cuff and other structures of the shoulder to cause pain;, and a list of the seven most common conditions follows:

7 most common shoulder conditions

• Shoulder bursitis: a bursa is a fluid-filled sac that acts as a cushion to prevent structures from rubbing against each other; the subacromial bursa in the shoulder is the largest bursa in the body, and when it becomes inflamed—often from regularly performing too many overhead activities—the result is shoulder bursitis; the most common symptom is pain at the top, front, and outside of the shoulder that gets worse with sleeping and overhead activity



• Rotator cuff tendinitis (shoulder tendinitis): the most common cause of shoulder pain, this condition results from irritation or inflammation of any of the rotator cuff tendons, which occurs gradually over time; the main symptoms are pain and swelling in the front of the shoulder and side of the arm, usually while raising or lowering the arm



• Shoulder impingement syndrome: a condition in which the bursa or any rotator tendons are trapped (or impinged) by the two main bones of the shoulder—the humerus and a piece of the scapula called the acromion—which is usually due to an outgrowth of bone (bone spur); symptoms include shoulder pain and weakness, and difficulty reaching up behind the back





• Note: Over time, shoulder impingement can lead to shoulder tendinitis and/or bursitis, and in some cases the names of these conditions are used interchangeably





• Rotator cuff tear: the result of one of the rotator cuff tendons detaching from the bone, either partially or completely; these injuries can occur either traumatically due to a single incident, or gradually over time, which is usually the case in older patients; the most common symptom is pain during the day and at night, and when lying on the shoulder or lifting or lowering the arm



• Frozen shoulder: a condition that occurs when scar tissue forms within the shoulder capsule, another structure that helps to keep the shoulder stable; this causes the shoulder capsule to thicken and tighten around the shoulder joint, which means there is less room for the shoulder to move normally, eventually causing it to “freeze;” symptoms include pain and stiffness that makes it difficult or impossible to move the shoulder



• Shoulder dislocation: an injury in which the ball of the shoulder (humerus) pops out of the socket (glenoid); this is typically due to a forceful motion, and the dislocation can be either partial or complete; symptoms include pain, swelling, and difficulty moving the shoulder



• Calcific tendinitis: a condition in which small deposits of calcium form within the tendons of the rotator cuff; calcific tendinitis is most commonly seen in individuals between the ages of 30-60 years, and the reasons it occurs are not entirely understood; in most cases it does not cause symptoms, but can lead to severe pain if the calcium deposits get bigger or become inflamed