MRI assessment of supraspinatus muscle volume.Supraspinatus atrophy was analyzed on most lateral image of scapular spine (arrowheads) in contact with scapular body (arrows) on oblique sagittal T1-weighted image. Imaginary line along inferior border of trapezius (T), distal clavicle (C), and scapula delineated supraspinatus fossa (dashed line). Occupation ratio of supraspinatus muscle in supraspinatus fossa was evaluated visually.