Intervertebral Disk of Fourth Lumbar Vertebra (L4–L5) (Discus intervertebralis L4–L5)
Educational content only — not medical advice.
Anatomy
The intervertebral disk of the fourth lumbar vertebra (L4–L5) is the most mobile and heavily stressed disk in the lumbar spine. Possessing substantial anterior height to sustain the lower lumbar lordosis, it undergoes continuous cyclical loading during flexion, extension, and weight-bearing activities.
Clinical notes
The L4–L5 disk is the single most common site of lumbar disc herniation (~45–50% of cases); posterolateral extrusion compresses the traversing L5 nerve root, producing severe sciatica, foot drop (extensor hallucis longus weakness), and sensory loss over the great toe.
Related structures
Educational references
FAQ
What is the role of the Intervertebral Disk of Fourth Lumbar Vertebra (L4–L5)?
The intervertebral disk of the fourth lumbar vertebra (L4–L5) is the most mobile and heavily stressed disk in the lumbar spine. Possessing substantial anterior height to sustain the lower lumbar lordosis, it undergoes continuous cyclical loading during flexion, extension, and weight-bearing activities.
Why is the Intervertebral Disk of Fourth Lumbar Vertebra (L4–L5) clinically important?
The L4–L5 disk is the single most common site of lumbar disc herniation (~45–50% of cases); posterolateral extrusion compresses the traversing L5 nerve root, producing severe sciatica, foot drop (extensor hallucis longus weakness), and sensory loss over the great toe.
Source & license
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