In the shoulder joint, the clavicle attaches to the scapula through the acromion, the bone on top of the shoulder. The joint at this location, called the acromioclavicular joint, can sometimes become narrowed and arthritic and spurs can form on the undersurface. This arthritic development can be due either to genetic osteoarthritis or overloading from weightlifting, years of push-ups, or years of overhead work and activity. When the joint is painful and not responsive to physical therapy or cortisone injections, it is helpful to open the joint space through a procedure called a Mumford procedure.