The shoulder joint does contain cartilage, which is fundamental to its ability to move smoothly and function properly.
Where Cartilage Resides in the Shoulder
The shoulder’s glenohumeral joint is a ball-and-socket joint where the humerus (upper arm bone) meets the glenoid fossa (socket) of the scapula (shoulder blade). Both the humeral head and glenoid fossa are covered by articular cartilage, also known as hyaline cartilage. This smooth tissue, only a few millimeters thick, provides a low-friction surface for movement.
Fibrocartilage forms the glenoid labrum, a cup-shaped rim of rubbery tissue attached around the glenoid socket. The labrum deepens the shallow glenoid cavity, creating a more secure fit for the humeral head, much like a bumper.
The Role of Shoulder Cartilage
Articular cartilage allows bones to glide with minimal friction, enabling a wide range of motion. This smooth surface also distributes forces across the joint, acting as a shock absorber. Its water content contributes to a spring-like quality, dissipating much of the load.
The glenoid labrum contributes to shoulder stability. By deepening the glenoid socket, it helps keep the humeral head cradled, reducing dislocation risk. The labrum also serves as an attachment point for ligaments and tendons, and distributes joint fluid for even load distribution.
Conditions Affecting Shoulder Cartilage
Various conditions can affect shoulder cartilage, leading to pain and limited movement. Osteoarthritis, a common type of arthritis, involves the gradual breakdown of articular cartilage. As cartilage thins, the protective covering for bones is lost, causing them to rub directly against each other. This results in pain, stiffness, and a grinding sensation, often progressing with age or due to injuries.
Labral tears are injuries to the glenoid labrum, the rim around the shoulder socket. These tears can occur from acute trauma, like a fall or dislocation, or from repetitive overhead movements in athletes. Common types include SLAP tears (Superior Labrum Anterior to Posterior), affecting the top labrum where the biceps tendon attaches, and Bankart lesions, tears in the lower labrum often associated with dislocations. Symptoms often include pain, instability, and a catching or grinding sensation.
Shoulder impingement syndrome, while primarily involving soft tissues, can indirectly affect cartilage over time. Repetitive impingement can lead to irritation and damage, potentially contributing to cartilage degeneration. Untreated articular cartilage damage can progress to osteoarthritis.