Pain and inflammation can occur in the shoulder area due to arthritis.
Osteoarthritis Arthritis may be caused by wear and tear. The pain and stiffness results from a degenerative condition in which the smooth outer covering of bones is damaged or completely worn down. This smooth outer covering is known as articular cartilage. When it no longer exists the bones and joints no longer slide and move without much friction. The resulting friction causes inflamation.
Rheumatoid arthritis a systemic inflammatory condition of the joint lining can also be the cause of pain. This condition affects multiple joints.
Arthritis can affect the acromion which causes the pain is centered in the back of the shoulder. But it can also affect another joint in the area called the acromioclavicular or AC joint which is located where the collarbone (clavicle) meets the tip of the shoulder bone (acromion). Arthritis in this joint results in pain usually at the front of the shoulder.