Lower back pain can be caused by a variety of problems with any parts of the complex, interconnected network of spinal muscles, nerves, bones, discs or tendons in the lumbar spine. Typical sources of low back pain include:
The large nerve roots in the low back that go to the legs may be irritated
The smaller nerves that supply the low back may be irritated
The large paired lower back muscles (erector spinae) may be strained
The bones, ligaments or joints may be damaged
An intervertebral disc may be degenerating