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