The part of the scapula that makes up the roof of the shoulder is called the acromion. In some ways, this joint is like any other joint. It has two bones that need to attach together, but needs to be flexible as well. The ends of the bones are covered with cartilage, a slick, rubbery surface that allows movement and protects the bones. This joint gets a lot of constant pressure as the arm is used overhead.
Weightlifters have an increased incidence of the conditon - at a younger age.
This may suggest that constant over head liting activities increase the stress on the joint. The arthritis may be the result of an old injury to the joint, such as an acromioclavicular separation . This injury is fairly common and can result from a fall on ther shoulder. The pain may be worse when the arm is brought across the chest, since this motion compresses the joint. The pain that occurs with this condition is a vague pain that may spread out to include the shoulder, the front of the chest, and the neck.