Fig. 1

Pfirrmann grading system for disc degeneration on sagittal T2 weighted images. a: Grade I, bright and homogeneous disc with clear distinction between nucleus pulposus and annulus fibrosis. Normal disc height. b: Grade II, inhomogeneous disc with horizontal dark band. Nucleus and annulus are clearly differentiated. Preserved disc height. c: Grade III, dark disc with unclear distinction between nucleus and annulus. Disc height is usually normal. d: Grade IV, dark and heterogeneous disc with decreased disc height. e: Grade V, dark and collapsed disc with no distinction between the nucleus and annulus