In the AMAGuides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, distal clavicle resection (resection arthroplasty of the acromioclavicular joint [ACJ]) results in ratable impairment, but only a single diagnosis within a region may be rated. Therefore, if another impairing condition is present in the shoulder region (eg, impingement syndrome or rotator cuff disease) only that resulting in the greatest causally related impairment is rated. In the setting of an occupational or other compensable injury or illness, causation of the impairment often is a key issue because, typically, only impairment that is causally related to the injury can be rated. For example, assume that a lifting injury at work caused a tear in a rotator cuff tendon that was already attenuated by repetitive impingement on inferiorly projecting spurs from longstanding degenerative arthritis of the ACJ. If surgery was performed for a traumatic rotator cuff tear and the distal clavicle also was resected due to preexisting ACJ arthritis, the latter surgery is not considered to be related to the injury. In other words, because the ACJ arthritis was neither caused nor worsened by the injury, this condition is not rated. The distal clavicular resection may have been warranted to diminish pain due to ACJ arthritis and/or eliminate the distal clavicle as a source of impingement.