Radiographic joint space in normal acromioclavicular joints.

The acromioclavicular joint space in standard antero-posterior images of 151 normal subjects was measured. The joint space was significantly wider in men. There was a highly significant reduction of the joint space with age in both men and women and in persons past 60 a joint space of 0.5 mm or less is not pathological. A joint space wider than 7 mm in men and 6 mm in women is abnormal. The measuring technique described is useful in population studies. In individual cases a simple measurement with a ruler serves the same purpose.