The shoulder joint contains the head of the humerus (upper arm bone) and the scapula (shoulder blade). The head of the humerus rides against the scapula in a tiny depression called the glenoid, much like a golf ball on a tee. The smaller size of the glenoid is what allows the wide range of motion in a healthy shoulder. The surfaces of the humerus and the glenoid are covered with a lubricating tissue called cartilage. The cartilage provides the shoulder joint frictionless, pain-free movement.
Osteoarthritis, the most common form of arthritis, is a wear and tear condition that destroys joint cartilage, and it typically develops after years of constant motion and pressure in the joints. As the cartilage continues to wear away, bone begins to rub against bone, causing the irritation, swelling, stiffness, and discomfort commonly associated with arthritis.
|Healthy Shoulder||Arthritic Shoulder|