The quadratus lumborum muscle sits in the small of the back to the side of the spine. It is enclosed in a fascial sheath. Following a blow to the back (such as a knee in the lumbar spine in footballers), this muscle can become tight and bound up within its fascia.
Why does it cause back pain?
The quadratus lumborum muscle connects the lumbar spine transverse processes to the pelvis. It is enclosed within a muscle sheath. The front of this sheath sits posterior to the sheath for the psoas muscle. The quadratus lumborum muscle moves the trunk to the side, hence tension in the muscle can create myofascial pain.
What can I do about it?
The quadratus lumborum will respond to massage and soft tissue treatment. As this muscle can spasm with other sources of low back pain, ongoing symptoms may require further assessment.
Do I need an X-ray or scan?
Not unless your doctor is trying to exclude other causes of back pain.