There are many causes. But there is one consistent issue which never helps: hip flexor mismanagement. The reason for this is hip flexors’ normal action can compress the nearby nerves and discs. So regardless of the back problem, imbalanced hip flexor complex is counterproductive.
The hip flexor complex origins run from the end of thoracic spine down the whole length of the lumbar spine and iliac crest. This gets confusing for people, because the discomfort of tension is generally experienced at the origin (back); but as we think about the flexor muscles we tend to focus on the front of the body and where they insert. Thus, A LOT of people forget the role of mobility through the quad and front of the hip as alleviating for the back.
The confusion leads people to move INTO hip flexion, which is categorically going to make long term prospects worse. Yesterday I saw a million-follower post on Instagram telling people to relieve back pain by “stretching” the quadratus lumborum. This is orthopedic nonsense. Like a forward fold hamstring stretch, the person doing it may get instant relief from the spastic pain in the over-fatigued and weak muscles. This is inevitable when lengthening them. A lengthened muscle can’t easily spasm. But lengthening over-fatigued and weak muscles merely further fatigues and damages them. We actually use this principle (called mechanical damage) in overfed and rested athletes to grow muscles. But in an already excessively stressed tissue, no positive adaptation is likely.
Look at the photo. The psoas minor crushes the low back into the pelvis. The psoas major smashes the spine down toward the femur. The ileacus jams the pelvis into the femur. Learn hip extension. Learn posterior pelvic tilt (https://www.instagram.com/p/BujDLHUnfhd/?igshid=128w4haitendh ). Learn neutral spine. Learn a little anatomy. Check some of my prior posts, including the ab series: 3/1-3/3/2019.