The Scapula and Acromioclavicular Joint Separation and Arthritis

Consensus is lacking for the diagnosis and optimal treatment of unstable acromioclavicular (AC) joint injuries. AC joint injuries have classically been understood and classified from a two-dimensional perspective dating back to the Rockwood classification. The current classification does not consider key clinical examination elements and the role of the scapula. More recent work highlights the three-dimensional form and function of the AC joint and role of the scapula with AC joint injuries. The clavicle serves a key role as a mobile strut for scapular and arm motion. The AC joint serves as a unifying link in the screw axis mechanism that governs normal scapulohumeral rhythm and the three-dimensional nature of the normal kinematics of the clavicle and scapula facilitate arm function.