Understanding Shoulder Pain

Most joints, including the shoulder, are free-moving synovial joints. Oily synovial fluid between both bone ends, which are covered by glassy cartilage, lubricates the joint. A capsule, reinforced by “straps” called ligaments, holds the joint together. With arthritis, the smooth functioning of this system is compromised.

There are two joints in the shoulder, and both may be affected by arthritis. One joint is located where the clavicle meets the tip of the shoulder blade (acromion). This is called the acromioclavicular (AC) joint. The glenohumeral joint is located where the head of the humerus fits into the scapula.

Osteoarthritis, also know as wear-and-tear arthritis, is a condition that destroys the smooth outer covering (cartilage) of the bone. As the cartilage wears away, it becomes frayed and rough, decreasing the protective space between the bones. When you move your shoulder, the bones of the joint rub against one another, causing pain.

Rheumatoid Arthritis is a chronic autoimmune disease. The joints of your body are covered with a lining, called synovium, that lubricates the joint and makes it easier to move. Rheumatoid arthritis causes the lining to swell, causing pain and stiffness in the shoulder joint.

Posttraumatic Arthritis is a form of osteoarthritis that develops after a joint is subjected to traumatic injury, such as a fracture or dislocation.

Avascular Necrosis (AVN) of the shoulder is a painful condition that occurs when the blood supply to the head of the humerus is disrupted. Because bone cells die without a steady blood supply, AVN can lead to destruction of the shoulder joint.

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

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

Bursitis often occurs in tandem with rotator cuff tendinitis. The many tissues in the shoulder can become inflamed and painful. Many daily activities, such as combing your hair or getting dressed, become difficult.

Trauma to the shoulder is common. Injuries range from a separated shoulder resulting from a fall onto the shoulder to a high-speed car accident that fractures the shoulder blade (scapula) or collarbone (clavicle). Fractures often cause severe pain, swelling and bruising about the shoulder.

Shoulder instability occurs when the head of the upper arm bone (the humerus) is forced out of the shoulder socket. Shoulder instability can happen as result of a sudden injury–such as a fall or during a contact sport such as football–or from overuse. Repetitive overhead sports such as volleyball and tennis can contribute to shoulder instability as well.   Occasionally, instability will be atraumatic, and occur with sleep or reaching in certain directions.

Traumatic dislocation can cause damage to the Glenoid labrum, which is a ring of collagen tissue that surrounds the shoulder socket, helping to deepen it and provide stability.

Some symptoms of labral tear include:

• Pain in the shoulder, especially with reaching overhead or behind the back
• A sense of subluxation, or sliding, of the joint with lifting objects
• Clicking or catching with movement or lifting
• A sense of numbness or tingling down the arm with throwing

As with any other injury, patients with symptoms that last for longer than one week should seek the care of one of our shoulder specialists.

A tendon is a flexible but inelastic cord of fibrous collagen tissue that connects muscle to bone. Tendons and muscles work together to control joint movement. When a muscle contracts, it pulls on the tendon, which then pulls the bone to cause movement. Tendinitis is a condition where the tendon become irritated and inflamed.

Generally, there are two types of tendinitis:

• Acute: Acute tendinitis results from overuse, such as from excessive ball throwing or other overhead activities during work or sport.
• Chronic: Chronic tendinitis results from repetitive, age-related wear and tear, as well as degenerative diseases like arthritis.

The most commonly affected tendons in the shoulder are the four rotator cuff tendons and one of the 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.

A tendon is a flexible but inelastic cord of fibrous collagen tissue that connects muscle to bone. Tendons and muscles work together to control joint movement. When a muscle contracts, it pulls on the tendon, which then pulls the bone to cause movement.

Tearing of tendons can result from acute injury or degenerative changes. Just as a frayed rope is vulnerable to breakage, so too are tendons that have weakened because of advancing age, long-term overuse, or general wear and tear. These tears may be partial or may completely separate the tendon from its attachment to bone. In most cases of complete tears, the tendon is pulled away from its attachment to the bone. Rotator cuff and biceps tendon injuries are among the most common of these injuries.

Your shoulder is made up of three bones: your upper arm bone (humerus), your shoulder blade (scapula), and your collarbone (clavicle). The shoulder is a ball-and-socket joint: the ball, or head, of your upper arm bone fits into a shallow socket in your shoulder blade.

Your arm is kept in your shoulder socket by your rotator cuff. The rotator cuff is a group of four muscles that come together as tendons to form a covering around the head of the humerus. The rotator cuff attaches the humerus to the shoulder blade and helps to lift and rotate your arm.

There is a lubricating sac called a bursa between the rotator cuff and the bone on top of your shoulder (acromion). The bursa allows the rotator cuff tendons to glide freely when you move your arm. When the rotator cuff tendons are injured or damaged, this bursa can also become inflamed and painful.

When one or more of the rotator cuff tendons is torn, the tendon no longer fully attached to the head of the humerus. Rotator cuff tears can be partial (an incomplete tear that damages the tendon but doesn’t completely sever it) or full-thickness (a complete tear that separates all of the tendon from the bone).

source: AAOS