Shoulder pain is an extremely common complaint. Up to 26% of the population is currently affected by it, and it ranks third—behind back pain and knee pain—in musculoskeletal conditions that lead people to consult their doctor. About 1% of the population visits a doctor for shoulder pain each year, and while the specific backstory may vary from patient to patient, most cases follow a relatively similar progression.

The causes of shoulder pain can generally be categorized into two groups: 1) traumatic (acute) injuries that damage certain structures of the shoulder immediately, 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 several types of shoulder issues.

Any component of the shoulder can be damaged in an acute or overuse injury, but most 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. Several problems can affect the rotator cuff or other structures within the shoulder to cause pain, stiffness, or other symptoms that lead to movement restrictions and activity limitations. To help you get a better sense of what can go wrong, here are six of the most common conditions that affect the shoulder:

6 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 may be used interchangeably
• Rotator cuff tear: this injury is the result of one of the rotator cuff tendons detaching from the bone, either partially or completely; it 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

Understanding red flags that could suggest an underlying problem

Regardless of what shoulder condition is present, in most cases, the best course of action is a comprehensive course of physical therapy. Physical therapists are movement experts whose goal is to guide patients back to full strength and function with an exercise–based approach. However, in rare cases, patients with certain urgent or severe conditions will require the care of another healthcare provider. To help you determine whether seeing a physical therapist is the right call, here are some potential red flags to be aware of if you’re dealing with shoulder pain:

• Deep, intense pain
• Pain associated with unexplained weight loss and/or fever
• Constant pain, including pain at night when the shoulder is at rest
• Signs of infection or septic arthritis (eg, pus or fluid, redness, fever, blisters, worsening swelling)
• Severe trauma to the shoulder that may have resulted in a fracture or dislocation
• Known or suspected cancer (eg, significant bone pain, which may be suggestive of a bone tumor)
• Persistent swelling and pain without any recent injury
• Severe muscle spasm

If you notice any of these red flags, see your primary care physician as soon as possible or—for traumatic injuries—go to the emergency department or urgent care clinic immediately. But in the absence of any red flags, we strongly recommend seeing a physical therapist for your shoulder pain as soon as possible to get started on a comprehensive treatment program that will help you regain your abilities over time.

In our next post, we’ll provide three of the best exercises to help keep your shoulders strong and reduce your risk for pain.