The Quadratus Lumborum (aka QL aka: coolest muscle named in the body) is a deep back muscle that connects the last rib, transverse processes of the lumbar spine and the iliac crest.
QL helps you 
side bend, extend and flex… but this dude will pull double time when there is some instability around the low back/pelvis- probably your glutes
not doing their thing.
The QL will absolutely wreck havoc on your low back when it’s short/tight and send referral pain all over the place
…okay not all over the place but certainly to your low back/glutes/hips.
Symptoms of QL dysfunction could include:
Pain running down the leg (sciatica) or
Pain referring into the hips, glutes, SI joint or even anteriorly into the groin
Painful side bending, twisting, forward bending
Pain when rolling side to side when lying down
Pain with coughing, sneezing, straining
It might also present as an obvious “hip hike” meaning one side of the pelvis is higher than the other