There are two joints in the shoulder and both may be affected by arthritis. The Acromioclavicular (AC) joint is where the clavicle meets the tip of the shoulder blade (acromion). The Glenohumeral joint is where the head of the humerus fits into the scapula.
Glenohumeral Arthritis is caused by the destruction of cartilage covering the bones in the glenohumeral joint. This causes bone-on-bone friction affecting the smooth movement of the shoulder. Glenohumeral Arthritis is most commonly seen in people over 50 years. It is estimated that it affects 20% of older population.