Which intervertebral disc level is most commonly herniated?

Which intervertebral disc level is most commonly herniated?

• A. L1-L2
• B. L2-L3
• C. L3-L4
• D. L4-L5

Answer: (D)

The main concept is that disc herniation tends to occur where the spine experiences the greatest mechanical stress and mobility. In the lumbar region, that peak is between L4 and L5, where substantial flexion–extension and axial load converge as the body moves and bears weight. The nucleus pulposus can bulge through a torn annulus fibrosus, and this is most likely to happen posterolaterally because that area offers less resistance than the central region. When a disc herniates at L4–L5, the affected nerve root is usually the L5 root, leading to radicular symptoms along the L5 distribution and possible dorsiflexion weakness. L5–S1 also sees herniation but is less common than L4–L5.

The main concept is that disc herniation tends to occur where the spine experiences the greatest mechanical stress and mobility. In the lumbar region, that peak is between L4 and L5, where substantial flexion–extension and axial load converge as the body moves and bears weight. The nucleus pulposus can bulge through a torn annulus fibrosus, and this is most likely to happen posterolaterally because that area offers less resistance than the central region. When a disc herniates at L4–L5, the affected nerve root is usually the L5 root, leading to radicular symptoms along the L5 distribution and possible dorsiflexion weakness. L5–S1 also sees herniation but is less common than L4–L5.