Quadratus Lumborum Muscle

Origin

The quadratus lumborum muscle originates from the:

- posterior half of the iliac crest;

- iliolumbar ligament.

Insertion

The fibers of the quadratus lumborum muscle travel superomedially and insert onto the:

- inferior border of twelfth rib;

- transverse processes of the first to fourth lumbar vertebrae.

Key Features & Anatomical Relations

The quadratus lumborum muscle is one of the muscles of the abdomen. It is a thick, quadrilateral type of skeletal muscle that contributes to the formation of the posterior abdominal wall.

It is located:

- anterior to the iliocostalis and transversus abdominis muscles;

- posterior to the kidneys, the colon, the psoas major muscle, the lateral arcuate ligament, and the iliohypogastric and ilioinguinal nerves;

- lateral to the lumbar vertebrae and the lumbar intertransversarii muscles.

Actions

The quadratus lumborum muscle is involved in multiple actions:

- during unilateral contraction, it laterally flexes the trunk to the same side;

- during bilateral contraction, it extends the trunk;

- it stabilizes the twelfth rib during inspiration (Standring, 2016).

List of Clinical Correlates

- Transmuscular quadratus lumborum block

References

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Actions

The quadratus lumborum muscle is involved in multiple actions:

- during unilateral contraction, it laterally flexes the trunk to the same side;

- during bilateral contraction, it extends the trunk;

- it stabilizes the twelfth rib during inspiration (Standring, 2016).