The interspinous ligament fills the space between adjacent spinous processes, complementing the supraspinous ligament above and the ligamentum flavum anteriorly to form the posterior ligamentous complex. It is the first ligament to fail during progressive spinal flexion overload after the supraspinous ligament, and its disruption is a sign of significant spinal instability that changes surgical management from decompression alone to decompression with fusion.
| Origin | Spinous process of each vertebra (inferior surface) |
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| Insertion | Spinous process of the vertebra below (superior surface) |
| Actions | Resists excessive spinal flexion; works with the supraspinous ligament as the posterior tension band of the spine |
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Interspinous ligament degeneration and cyst formation are increasingly recognised causes of central spinal stenosis and neurogenic claudication. Interspinous process devices are implanted between adjacent spinous processes under the interspinous ligament as minimally invasive treatments for lumbar spinal stenosis, aiming to limit extension at the symptomatic level.
Tearing from excessive flexion loading producing midline spinal pain directly over the involved spinous processes, a sign of significant posterior ligamentous complex injury that may require surgical stabilisation.
