Lumbar vertebra L5

Function

Sits like a keystone at the lumbosacral angle, transferring the whole upper-body load onto the sacrum. The L5 root supplies the gluteus medius, toe extensors and lateral leg skin.

Landmarks

• Wedge-shaped body
• Thick transverse processes
• Lumbosacral angle

Articulations (joints)

• L4 above
• Sacrum (lumbosacral joint)

Clinical relevance

Spondylolisthesis — L5 slipping forward on the sacrum — is common here; L5–S1 disc herniation presses the S1 root, killing the ankle jerk.