Shoulder pain

Shoulder Pain and Common Shoulder Problems

What most people call the shoulder is really several joints that combine with tendons and muscles to allow a wide range of motion in the arm — from scratching your back to throwing the perfect pitch.

Mobility has its price, however. It may lead to increasing problems with instability or impingement of the soft tissue or bony structures in your shoulder, resulting in pain. You may feel pain only when you move your shoulder, or all the time. The pain may be temporary, or it may continue and require medical diagnosis and treatment.

The shoulder is a ball-and-socket joint made up of three bones:

• The humerus (upper arm bone)
• The scapula (shoulder blade)
• The clavicle (collarbone)

The head of the upper arm bone fits into a rounded socket in the shoulder blade. This socket is called the glenoid. A combination of muscles and tendons keeps your arm bone centered in your shoulder socket. These tissues are called the rotator cuff. They cover the head of the upper arm bone and attach it to the shoulder blade.

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Most shoulder problems fall into four major categories:

• Tendon inflammation (bursitis or tendinitis) or tendon tear
• Instability
• Arthritis
• Fracture (broken bone)

Other much less common causes of shoulder pain are tumors, infection, and nerve-related problems.

Bursae are small, fluid-filled sacs that are located in joints throughout the body, including the shoulder. They act as cushions between bones and the overlying soft tissues, helping to reduce friction between the gliding muscles and the bone.

Sometimes, excessive use of the shoulder leads to inflammation and swelling of the bursa between the rotator cuff and part of the shoulder blade known as the acromion. The result is a condition known as subacromial bursitis.

Bursitis often occurs in association with rotator cuff tendinitis. The pain and inflammation can make many daily activities, such as combing your hair or getting dressed, difficult.

A tendon is a cord that connects muscle to bone. Tendinitis is a result of inflammation in the tendon.

Generally, tendinitis is one of two types:

• Acute. Excessive ball throwing or other overhead activities during work or sport can lead to acute tendinitis.
• Chronic. Degenerative diseases like arthritis or repetitive wear and tear, can lead to chronic tendinitis.

The most commonly affected tendons in the shoulder are the four rotator cuff tendons and one of the two biceps tendons. The rotator cuff is made up of four small muscles and their tendons that cover the head of your upper arm bone and keep it in the shoulder socket. Your rotator cuff helps provide shoulder motion and stability.

Splitting and tearing of tendons may result from:

• Acute injury
• Degenerative changes in the tendons due to advancing age, long-term overuse, or wear and tear

These tears may:

• Be partial (only go through part of the tendon thickness)
• Completely separate the tendon (pull it away) from where it attaches to bone

Rotator cuff and biceps tendon injuries are among the most common of these injuries.

Shoulder impingement occurs when the top of the shoulder blade (acromion) puts pressure on the underlying soft tissues when the arm is lifted away from the body. As the arm is lifted, the acromion rubs, or "impinges" on, the rotator cuff tendons and bursa. This can lead to bursitis and tendinitis, causing pain and limiting movement. 

Shoulder instability occurs when the head of the upper arm bone is forced out of the shoulder socket. This usually happens initially as a result of a sudden injury, but it can become chronic.

• Shoulder dislocations can be partial, with the ball of the upper arm coming just partially out of the socket. This is called a subluxation.
• A complete dislocation means the ball comes all the way out of the socket.

Once the ligaments, tendons, and muscles around the shoulder become loose or torn, dislocations can occur repeatedly. Recurring (repeated) dislocations, which may be partial or complete:

• Cause pain and unsteadiness when you raise your arm or move it away from your body
• Lead to an increased risk of developing arthritis in the joint

Shoulder pain can also result from arthritis. There are many types of arthritis. The most common type of arthritis in the shoulder is osteoarthritis, also known as wear-and-tear arthritis. Symptoms such as pain and stiffness typically begin during middle age. Osteoarthritis develops slowly and the pain it causes worsens over time.

Osteoarthritis may be related to sports or work injuries or chronic wear and tear. Other types of arthritis can be related to rotator cuff tears, infection, or an inflammation of the joint lining.

Often people will avoid shoulder movements to try to lessen arthritis pain. This sometimes leads to a tightening or stiffening of the soft tissue parts of the joint, resulting in a painful restriction of motion.