Distal clavicular osteolysis affects the acromioclavicular joint (AC joint) at the top of the shoulder joint. As we mentioned previously, this condition involves the gradual destruction of the bone tissue in the AC joint. The AC joint is where part of the shoulder blade meets the distal end of the collarbone, or clavicle. The acromioclavicular ligament connects these two bones together, which allows us to raise our arms over our heads.