Acromioclavicular Joint Arthritis of the Shoulder

The AC joint is located at the tip of the shoulder where the shoulder blade (scapula) and collarbone (clavicle) come together at a point on the upper prut of the shoulder blade called the acromion. These two bones are held together by ligaments. One group of ligaments envelope the joint to form a capsule, that covers the joint; these ligaments are termed the acromioclavicular ligaments. Another set of ligaments stabilize the shoulder by holding the clavicle in place by attaching it to a bony projection on the surface of the shoulder blade called the coracoid process.  These ligaments are called the coracoclavicular ligaments. There is a disk of cartilage in the joint between the two bones that helps guide the joint involvement. As you move your shoulder, the AC joint allows movement to occur between the clavicle and scapula.
What is Acromioclavicular Joint Arthritis of the Shoulder?
AC joint arthrosis, or osteoarthritis of the, acromioclavicular joint is most common in people who are middle aged. It develops when the cartilage in the AC joint begins to wear out. With this condition, there usually pain that limits the motion of the arm.
Causes of AC Arthritis of the Shoulder
The principal cause of AC joint arthrosis is wear and tear due to use.  As a person uses his/her arm and shoulder, stress is placed on the joint. This stress produces wear and tear on the cartilage, the cartilage becomes worn over time, and eventually arthritis of the joint may occur.  Persons who must use their arms for extended periods of time rue susceptible to AC joint arthrosis.  Constant overhead lifting, such as is engaged in by weightlifters or construction workers who work overhead, can increase the incidence of the disease. Other susceptible individuals are athletes participating in contact sports or engaging in any activity that may result in a fall on the end of the shoulder.
Symptoms of AC Arthritis of the Shoulder
One of the first signs that a person may have arthrosis of the AC joint is pain and tenderness at the top of the shoulder around the joint. Sleeping on the side may cause pain. There may be a decrease in shoulder motion.  Compression of the joint, such as bringing the arm across the chest may result in increased pain. There may be some swelling at the site of the joint. If the AC joint had been injured some time in the past, there may be a snap or click as the shoulder is moved, and the area of the AC joint may become more prominent.
Usually the diagnosis of AC joint arthrosis is made during the doctor's physical examination.  In the course of the examination, the doctor will look for tenderness over the AC joint and the presence of pain with compression of the joint.  The doctor may determine that an injection of a local anesthetic,. such as lidocaine, is indicated.  The injection will reduce the pain temporarily and confirm the diagnosis.  X-rays may be used to reveal a narrowing of the joint and the presence of bone spurs around the joint.