The quadratus lumborum is a rectangular muscle filling the space between the iliac crest and the 12th rib on each side of the lumbar spine, connecting the pelvis to both the lumbar vertebrae and the lowest rib. It is a deep stabiliser of the lumbar spine and pelvis, active in virtually all upright movements, and one of the most consistently implicated muscles in non-specific low back pain. Its trigger points produce some of the most referred pain patterns in the body.
| Origin | Posterior iliac crest and iliolumbar ligament |
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| Insertion | Inferior border of the 12th rib; Transverse processes of L1 through L4 |
| Nerve Supply | Subcostal nerve (T12); Ventral rami of L1 through L3 |
| Blood Supply | Lumbar arteries; Iliolumbar artery |
| Actions | Lateral flexion of the lumbar spine to the same side; Extension of the lumbar spine when acting bilaterally; Fixation of the 12th rib during forced expiration and breathing; Elevation of the ilium during gait to allow the contralateral foot to clear the ground |
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During single-leg stance and walking it elevates the ipsilateral pelvis to allow the swing-phase limb to clear the floor, a function that becomes critical when the hip abductors are weak and the quadratus lumborum must compensate by hiking the pelvis rather than stabilising it.
Quadratus lumborum myofascial trigger points refer pain to the lateral hip, buttock, and groin in patterns that closely mimic trochanteric bursitis, sacroiliac joint pain, and hip pathology. It is often unrecognised because it is not accessible to standard surface palpation and requires deep lateral pressure with the patient side-lying or prone. Bilateral QL overactivity is a common finding in people with lumbar hyperlordosis and anterior pelvic tilt.
The QL is not accessible through direct surface palpation but can be reached with firm deep pressure applied just lateral to the erector spinae mass, immediately above the iliac crest, with the patient positioned side-lying with the top hip slightly flexed.
Acute muscle fibre tears from sudden lateral bending or rotation under load, producing sharp unilateral lower back pain that limits lateral movement and is reproduced by resisted lateral flexion.
Trigger points producing lateral hip, buttock, and groin pain that mimics several other diagnoses, managed with dry needling, manual therapy, and addressing the underlying pelvic control deficits.
