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[Skeletal system](https://durgical.com/en/anatomy/system/skeletal-system/) · [Spine](https://durgical.com/en/anatomy/region/spine/)

# L4 vertebra

L4 is the fourth lumbar (lower-back) vertebra; its large body carries the weight of the upper body and lets the lower back bend.

Official name: L4

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## What it is

A large lower-back vertebra with a thick [kidney](https://durgical.com/en/anatomy/kidney/) -shaped body built to carry weight.

## What it does

Carries the weight of the upper body and, with the disc and facet joints, lets the lower back bend forward and back.

## Key points

- Lumbar puncture and spinal anesthesia use the L3–L4 or L4–L5 gap, well below the end of the cord; the iliac crest line guides this but can be off by a level
- L4–L5 is the commonest lumbar herniation level: a posterolateral herniation hits the traversing [L5 nerve root](https://durgical.com/en/anatomy/l5/), a far-lateral one the exiting [L4 nerve root](https://durgical.com/en/anatomy/l4/)
- Degenerative spondylolisthesis at L4–L5 keeps the pars intact, so the slipping arch narrows the canal and causes neurogenic claudication

## Key facts

**Joints with**
L3 above and L5 below (intervertebral discs, facet joints)

**Landmarks**
Large kidney-shaped body; no costal facets or transverse foramina; mammillary processes; [spine](https://durgical.com/en/anatomy/region/spine/) on the iliac crest line (supracristal or Tuffier line); aortic bifurcation at L4

## Relations

**In front**
[Abdominal aorta](https://durgical.com/en/anatomy/abdominal-aorta/) dividing into the [common iliac arteries](https://durgical.com/en/anatomy/common-iliac-artery/); the [common iliac veins](https://durgical.com/en/anatomy/common-iliac-vein/) join to form the [inferior vena cava](https://durgical.com/en/anatomy/inferior-vena-cava/) a little lower and to the right (L5)

**Lateral**
[Psoas major](https://durgical.com/en/anatomy/psoas-major/) with the [lumbar plexus](https://durgical.com/en/anatomy/lumbar-plexus/) inside it; the iliac crest lies at the side at about this level

**Behind**
[Low-back facet joints](https://durgical.com/en/anatomy/zygapophysial-joints-spine-and-pelvis/) and the [ligamentum flavum](https://durgical.com/en/anatomy/ligamenta-flava/); [multifidus](https://durgical.com/en/anatomy/multifidus-muscles/), the bulkiest deep back muscle at the lower levels

**Contents**
[Cauda equina](https://durgical.com/en/anatomy/cauda-equina/) in the dural sac: the L5 roots run down toward their foramen while the L4 roots leave at the L4–L5 foramen

## How to find it

With the person sitting or lying curled forward, the hands rest on the tops of both iliac crests and the thumbs meet in the midline at about the L4 spine or the L4–L5 gap. The gap is felt as a soft dip between two spines that opens as the back flexes.

## Examination

- Straight leg raise: leg pain between about 30° and 70° of hip flexion suggests tension on the L5 or S1 root; pain in the sciatic leg on raising the other leg (crossed SLR) is more specific
- L5 root: weak [big toe](https://durgical.com/en/anatomy/great-toe/) extension and heel walking, numb top of the foot; no reliable reflex

## On imaging

Standing lateral and flexion-extension films show slip and instability; MRI shows the disc, the canal and the roots, with axial slices showing which root is touched.

## Common problems

- Disc degeneration and herniation at [L4-L5](https://durgical.com/en/anatomy/l4-l5/), the most common level for back and leg pain.
- Degenerative spondylolisthesis: L4 slips forward on L5, often with stenosis (more common in women over 50).
- Spinal stenosis: the canal narrows from disc bulging, facet arthritis and a thick ligamentum flavum.
- Compression fractures from osteoporosis or injury.

## How it is diagnosed

X-rays (standing, and bending forward and back) show alignment and slipping. MRI shows discs, nerves and stenosis. CT shows bone detail.

## Treatment

- Most back pain improves with staying active, physical therapy and pain medicine.
- Stenosis with leg pain when walking that does not improve: decompression (laminectomy).
- Slipping with instability: decompression plus fusion with screws, rods, a cage and bone graft.

## Clinical notes

- Neurogenic claudication from stenosis eases with sitting or bending forward (leaning on a shopping cart), unlike vascular claudication, which eases with standing still and comes with weak pulses
- Large central herniations at L4–L5 can compress the whole cauda equina: saddle numbness, urinary retention and bilateral leg weakness, a surgical emergency

## Related conditions

- [Spondylolisthesis](https://durgical.com/en/conditions/spondylolisthesis/)
- [Vertebral osteomyelitis](https://durgical.com/en/conditions/vertebral-osteomyelitis/)
- [Achondroplasia](https://durgical.com/en/conditions/achondroplasia/)
- [Lumbar Disc Herniation](https://durgical.com/en/conditions/lumbar-disc-herniation/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which spinal level does the line joining the tops of the iliac crests (Tuffier line) usually cross?

The L4 spine or the L4–L5 gap; it guides lumbar puncture and spinal anesthesia but can be off by a level.

## At L4–L5, which nerve root does a posterolateral herniation hit, and which does a far-lateral herniation hit?

Posterolateral: the traversing L5 nerve root. Far-lateral: the exiting L4 nerve root.

## How is neurogenic claudication from L4–L5 stenosis told apart from vascular claudication?

Neurogenic claudication eases with sitting or bending forward; vascular claudication eases with standing still and comes with weak pulses.

## What does leg pain on a straight leg raise between about 30° and 70° suggest?

Tension on the L5 or S1 nerve root; pain in the sciatic leg on raising the other leg (crossed SLR) is more specific.

## Which major vessel divides in front of the L4 vertebra?

The abdominal aorta, into the common iliac arteries.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
vertebra lumbalis IV TA2 1068

**Official Spanish (DeCS)**
Vértebra lumbar L4 DeCS D008159

**English (TA2)**
L4

## Related

- [L3–L4 disc](https://durgical.com/en/anatomy/l3-l4/)
- [L4–L5 disc](https://durgical.com/en/anatomy/l4-l5/)
- [Lumbar arteries](https://durgical.com/en/anatomy/lumbar-arteries/)
- [Anterior longitudinal ligament](https://durgical.com/en/anatomy/anterior-longitudinal-ligament/)
- [Endplates](https://durgical.com/en/anatomy/vertebral-endplates/)
- [Low-back facet joints](https://durgical.com/en/anatomy/zygapophysial-joints-spine-and-pelvis/)
- [Iliolumbar ligament](https://durgical.com/en/anatomy/iliolumbar-ligament/)
- [Interspinales](https://durgical.com/en/anatomy/interspinales-muscles/)

Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=8334&filter=ths_termall&q=V%C3%A9rtebras%20Lumbares); [Anatomy, Back, Lumbar Spine](https://www.ncbi.nlm.nih.gov/books/NBK557616/).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l4/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/lumbar-vertebra-spine-and-pelvis-l4/