Human Movement Science & Functional Anatomy of the:

Quadratus Lumborum

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.
  • Action:
    • 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).

Integrated Function:

  • 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.
  • Synergists:
    • The QL is the prime mover of lateral flexion, with the internal obliques, external obliques, ipsilateral erector spinae, and to a lesser degree the ipsilateral latissimus dorsi acting synergistically.
    • The QL may be a synergist for lumbar extension, although it is likely that it can only assist post initiation of extension and only to a small degree.  The primary lumbar extensor is the erector spinae.
    • The internal obliques are synergists for lateral flexion of the spine, again likely third in ability to produce force behind the external oblique, and prime mover quadratus lumborum.
    • The QL, despite its relatively deep position within the trunk musculature, is likely a global stabilizer of the lumbar spine, acting synergistically with other global stabilizers (rectus abdominis, external obliques, internal obliques, erector spinae) when loads increase beyond what a well functioning intrinsic stabilization subsystem can handle.   Further, this muscle plays a role in stabilization of the sacroiliac joint as a stabilizer of the lumbar spine and ilium.  Sacroiliac joint dysfunction (SIJD) often results in over-activity, trigger point development, and adaptive shortening of the quadratus lumborum on the dysfunctional side, implying that synergistic dominance of the global stabilization system may be a precursor-to, or

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