Human Movement Science & Functional Anatomy of the:
by Brent Brookbush MS, PES, CES, CSCS, ACSM H/FS
Quadratus Lumborum (QL):
- Origin: Iliolumbar ligament, iliac crest, and occasionally from upper borders of the transverse processes of the lower three or four lumbar vertebrae (11).
- Insertion: The inferior border of the last rib and transverse processes of the upper four lumbar vertebrae (11).
- The quadratus lumborum is bordered by the deepest layer of the thoracolumbar fascia and psoas anteriorly and the middle layer of the thoracolumbar fascia and erector spinae posteriorly. The lateral border of the quadratus lumborum may be palpated (easiest in prone) by using your index fingers to find the transverse processes of LI and L5, and your thumbs to find the edge of the 12th rib and posterior crest of ilium. This creates a square that borders the QL. Slide your thumbs toward one another. Use slow firm pressure to sink your thumbs deep and medially and you should feel the edge of the QL. If you are unsure have the person you are palpating hip hike; the QL should pop into your fingers (14).
- Nerve: Lumbar Plexus via nerve roots L1-L3 and sometimes T12.
- Primary lateral flexor of the lumbar spine, this may also result in relative hiking of the ipsilateral pelvis
- Weak extensor of the lumbar spine
- Depresses 12th rib; acting bilaterally during respiration, it fixes the last 2 ribs to improve the efficiency of the diaphragm.
- Although there is some debate over the precise role (intrinsic stabelizer or global mover) of this muscle, studies have shown this muscle to be active during "anti-buckling" activities, such as walking while carrying heavy buckets of water (13).
- Stabilization: Stabilization of the lumbar spine, 12th rip, and sacroiliac joint.
- Eccentrically Decelerates:
- Eccentric deceleration of contralateral flexion of the lumbar spine (anti-buckling)
- Eccentric decelerates of flexion of the spine.