CorpusHuman Anatomy
SkeletalBone group

Lumbar vertebrae

Vertebrae lumbales

Also known as: L1–L5, lumbar spine

The five largest vertebrae (L1–L5), in the lower back, built to bear the weight of the upper body. They have massive kidney-shaped bodies and lack transverse foramina and costal facets.

Show on body map Muscles — Posterior View

Overview

Number5
Supracristal plane (iliac crests)L4 spinous process / L4–L5 interspace
Commonest disc herniationsL4–L5 and L5–S1 (≈95% of lumbar)

Lumbar vertebrae have large, kidney-shaped bodies, short thick pedicles and laminae, a triangular vertebral foramen (smaller than cervical, larger than thoracic), long slender transverse processes, and short, thick, hatchet-shaped (quadrangular) spinous processes projecting horizontally backward — leaving gaps between laminae that are used for lumbar puncture. The superior articular processes bear a mammillary process, and an accessory process lies at the base of each transverse process (attachments of multifidus and intertransversarii).

The articular facets lie in a roughly sagittal plane (superior facets concave and facing medially, inferior facets facing laterally), so they permit flexion–extension and lateral flexion but strongly resist rotation. L5 has the largest body, wedge-shaped (taller anteriorly), contributing to the lumbosacral angle, and massive transverse processes attached to the ilium by the iliolumbar ligaments. The spinal cord ends at L1–L2; below this the vertebral canal contains the cauda equina within the dural sac (to S2).

Location

Lower back, between T12 and the sacrum.

Parts & subdivisions

  1. Kidney-shaped body
    Largest of the column; L5 wedge-shaped.
  2. Hatchet-shaped spinous processes
    Short, thick, horizontal — wide interlaminar gaps.
  3. Sagittally oriented facets
    Resist rotation; allow flexion–extension.
  4. Mammillary and accessory processes
    Attachments of deep back muscles.
  5. Pars interarticularis
    Site of spondylolysis, most often L5.

Anatomy

Articulations

T12 above, sacrum (lumbosacral joint) below; discs and facet joints.

Ligaments

Iliolumbar ligaments (L5 transverse processes to iliac crest), anterior and posterior longitudinal ligaments, ligamenta flava, interspinous and supraspinous ligaments.

Function

  • Bear the weight of the head, upper limbs and trunk
  • Allow flexion and extension of the lower back
  • Protect the cauda equina

Clinical significance

Lumbar disc herniation

Posterolateral prolapse compresses the traversing root: L4–L5 → L5 (big-toe extension weakness, dorsum of foot), L5–S1 → S1 (ankle jerk lost, lateral foot, plantarflexion). Straight-leg raise reproduces sciatica.

Lumbar spinal stenosis

Degenerative narrowing (facet hypertrophy, ligamentum flavum buckling, disc bulging) causes neurogenic claudication — leg pain on walking relieved by flexion (sitting, leaning on a shopping trolley).

Lumbar puncture

Needle inserted in the midline at L3–L4 or L4–L5 with the spine flexed to open the interlaminar spaces.

Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.