Which spinal level showed complete disc collapse on imaging?

• A. L4-L5
• B. L5-S1
• C. L3-L4
• D. L2-L3

Answer: (B)

Complete disc collapse on imaging reflects advanced degenerative change at the level that bears the most load. The lowest lumbar segment, L5-S1, carries the greatest axial and shear forces from the upper body and gait. Over time, this mechanical stress accelerates disc dehydration and collapse of height. On imaging, this level tends to show the most pronounced, and often complete, loss of disc space compared with higher lumbar levels. In plain X-ray you’d see the disc space between L5 and S1 markedly reduced; MRI would confirm with loss of disc signal and possible endplate changes, consistent with severe degeneration. The other levels can degenerate, but complete collapse is most characteristic at the lumbosacral junction due to its role as the transition point between the mobile lumbar spine and the fixed sacrum.