Shoulder Joint Overview

Below are links to the topics discussed on this page to give a helpful and general overivew of shoulder surgery.

• How The Shoulder Works
• Causes of Shoulder Pain

If you have persistent pain, catching, or swelling in your knee, a procedure known as arthroscopy may help relieve these problems.

Understanding How Shoulders Work

A joint is formed by the ends of 2 or more bones that are connected by thick bands of tissue called ligaments. The shoulder typically involves 2 bones:

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

The rotator cuff – 4 muscles connecting the humerus with the scapula – supplies stability and balance to the shoulder joint. Proper rotator cuff balance is essential for arm raising and rotation. When you raise your arm, the rotator cuff holds the humeral head tightly within the socket (glenoid) of the scapula.

A smooth substance called articular cartilage covers the surface of the bones where they touch each other within a joint. This articular cartilage acts as a cushion between the bones. In addition, lubricated sacs of tissue called bursae (singular: bursa) also protect muscles and tendons, allowing them to slide against each other with less friction.

In the shoulder, one of these bursae is located between the rotator cuff and the acromion – the part of the scapula that "roofs" the shoulder. As with other joints, the remainder of the shoulder joint surface is covered by a thin, smooth tissue liner called synovial membrane, which makes a small amount of fluid that acts as a lubricant so that the joint bones will not rub against each other.

Causes of Shoulder Pain

One of the most common causes of shoulder pain is arthritis. The most common types of arthritis are:

• Osteoarthritis (OA) — sometimes called degenerative arthritis because it is a "wearing out" condition involving the breakdown of cartilage in the joints. When cartilage wears away, the bones rub against each other, causing pain and stiffness. The most common cause of shoulder replacement, OA can occur without a shoulder injury, but this seldom happens since the shoulder is not a weight-bearing joint like the knee or shoulder. Instead, shoulder OA commonly occurs many years following a shoulder injury, such as a dislocation, that has led to joint instability and repeated shoulder dislocations, damaging the shoulder joint so that OA develops. When the resulting joint pain and stiffness become severe enough to affect a person's daily life and comfort, shoulder replacement may be recommended.


• Post-traumatic Arthritis — may develop after an injury to the joint in which the bone and cartilage do not heal properly. The joint is no longer smooth, and these irregularities lead to more wear on the joint surfaces.


• Rheumatoid Arthritis (RA) — produces chemical changes in the synovium that cause it to become thickened and inflamed. In turn, the synovial fluid destroys cartilage. The end result is cartilage loss, pain, and stiffness. RA affects women about 3 times more often than men, and may affect other organs of the body.

Other shoulder pain causes include avascular necrosis, which can result when bone is deprived of its normal blood supply (for example, after organ transplantation or long-term cortisone treatment), and deformity or direct injury, such as a fracture, to the joint.

In some cases, joint pain is made worse by the fact that a person will avoid using a painful joint, weakening the muscles and making the joint even more difficult to move.

What's causing your shoulder joint pain? Is getting relief through joint replacement an option for you? These are just some of the answers that an orthopaedic surgeon can provide. But first, it's a good idea to be sure you have information about joint replacement that will help you understand what the surgeon tells you.