The "Tangent Sign"

You may find this sign helpful in assessing significant supraspinatus muscle atrophy via MRI. On your selected T1 SE parasagittal image draw a tangent connecting the tips of the spine of the scapula and acromion process. If muscle mass extends above the tangent: positive sign. If muscle mass lies below the tangent: negative sign. A negative tangent sign indicates significant supraspinatus atrophy. Reference: Invest Rad (1998)163-170.