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Lumbar Facet Joints (Detail)

articulationes zygapophysiales lumborum (detail)

The lumbar zygapophyseal joints have a sagittal orientation (superior-inferior) that allows flexion-extension while severely limiting rotation, explaining why lumbar rotation injuries require disc or ligament failure rather than just facet failure. Lumbar facet pain accounts for 15-40% of chronic low back pain. The L4-L5 and L5-S1 facets bear the highest loads and are the most common pain generators.

Anatomical Data

Structure

Bones	Superior articular process of the lower lumbar vertebra, concave, sagittal orientation Inferior articular process of the upper lumbar vertebra, convex, sagittal orientation
Ligaments	Facet joint capsule (strongest posteriorly where it is taut in flexion) Ligamentum flavum (medial capsule equivalent) Interspinous and supraspinous ligaments

Biomechanics

Function & Actions

Movements	Flexion-extension (primary lumbar motion, up to 50 degrees total) Minimal rotation (1-2 degrees per level due to sagittal orientation) Lateral flexion (5-8 degrees per level)

Clinical Relevance

Clinical Notes

Lumbar facet pain is suspected when back pain (with possible referred pain to the buttock and posterior thigh but not below the knee) is worsened by extension and rotation and relieved by flexion. Diagnosis is confirmed by medial branch block (>50% relief). Two positive blocks are required before radiofrequency neurotomy, which provides 6-12 months relief.

Pathology

Common Injuries & Conditions

Lumbar Facet Syndrome

L4-L5 and L5-S1 facet joint pain producing extension-worsened low back and buttock pain confirmed by medial branch block and managed with RF neurotomy.

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