Quadratus Lumborum (QL) :
often referred to as our 'Hip Hiker' muscle ! Can also be seen as a really deep abdominal muscle
OR a really deep back muscle so I guess it's in the middle of us!
(image on left c/o Trail Guide to the Body)
QL muscle attachment points:
QL attaches to the top of our hip (close to the spine) then climbs up the lumbar spine (vertebrae) and finally attaching to our 12th (bottom) rib :
Origin: the medial half of the inferior border of the 12th rib* and the transverse processes of the Lumbar vertebrae 1-4**
Insertion: Iliac crest and ilio-lumbar ligament***
Break it down further:
* medial half meaning closer to our spine (instead of away from it) and inferior border meaning underneath. The 12th rib is shorter than the rest and is considered a 'floater' as this rib does not wrap around your torso attaching to the front like the higher ribs.
**the transverse processes (aka TVPS) of our vertebrae are the bones that stick out on either side (kinda like wings!) Often when a muscle attaches to sides of our spine like that - the muscle will help bend to the side (aka lateral flexion)
***iliac crest aka the top curve of our hip & the ilio-lumbar ligament spans between the hip bone to the lumbar vertebrae bone.
(original image on left c/o Trail Guide to the Body)
QL Muscle Actions:
Unilaterally (each QL on their own):
a-laterally tilts the pelvis (aka hip hike)
b-lateral flexion of spine (vertebral column) to the same side (a side bend)
c- assists in extension of the spine (aka a back bend)
these movements are moving the trunk of our body and the movement is happening at the spinal joints.
Bilaterally (both QLs together) :
When breathing - QLs secure (hold down) the 12th rib during inspiration (inhalation) and forced exhalation.
One QL gets shortened in Scoliosis
(a postural condition when one hip hikes, creating an 'S' curve or our spine)
scoliosis image via Gary Leung
Personally I've had on and off issues with my Right QL for years. It basically feels like a dull, low right back pain). It only goes away when I exercises regularly/consistently - and of course regular massage, heat application and posture awareness! (I have a nasty habit of favouring one hip / leg when standing, and crossing my legs when sitting - helping encourage my own hip hike over time!)
All of this makes me a huge fan of receiving and GIVING deep low back massage (!)