Quadratus Lumborum - Muscle Physiology & Functional Anatomy

Anatomy

Origin:

• Posterior inner lip of iliac crest & iliolumbar ligament
  

Insertion:

• Transverse processes of the upper 4 lumbar vertebrae & the lower border of 12th (last) rib

Major Arteries:

• Lumbar arteries

• Lumbar branch of iliolumbar artery

Neural Innervation:

• Lumbar nerves L1-L4

• Subcostal nerve (T12)

Trigger Points:

Physiology

Concentric Functions:

• Lateral flexion of the spine & extension of the lumbar spine (w/ bilateral contraction)

Eccentric Functions:

• Dynamically stabilizes lumbo-pelvic hip complex

Isometric Function:

• Dynamically stabilizes lumbo-pelvic hip complex

Related Muscles

• Internal Obliques

• External Obliques

• Iliopsoas

• Erector Spinae

Antagonists:

• Rectus Abdominis

Exercises:

• Side Bends

More Images of the Quadratus Lumborum Muscle

More Information about the Quadratus Lumborum Muscle

The quadratus lumborum muscle is one of the important deep muscles in the lubmo-pelvic hip complex.  In addition to its 2 concentric functions stated above the quadratus lumborum fixes the 12th rib during forced expiration and evetates the ilium during an ipsilateral (on the same side) contraction.

Since the quadratus lumborum connects the pelvis to the spine it is a common source of low back pain for a variety of reasons including increasing the propensity for strains to the the erector spinae muscles as well as having spasms in the quadratus lumborum muscle itself due to overuse.

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