Lumbar pain extending to the buttocks and thighs may be caused by lumbar disc herniation, lumbar spinal stenosis, and sciatic nerve injury. 1. Lumbar disc herniation: Lumbar disc herniation is caused by rupture of the annulus fibrosus, protrusion of the nucleus pulposus, and compression of the peripheral nerve roots, causing sciatica, which can be characterized by lumbar pain, as well as pain and numbness in the buttocks, thighs, and outer calves. 2. Lumbar spinal stenosis: Lumbar pain is caused by lumbar spinal stenosis, which is due to the compression of the nerve roots caused by lumbar spinal stenosis, which leads to sciatic nerve compression, resulting in pain in the buttocks and legs. 3. Sciatic nerve injury: the nerve roots of the lumbar spine form the sciatic nerve after the nerve root, when the nerve root is compressed or damaged, it leads to low back pain to the buttock extending to the thigh. There are many reasons for the symptoms of low back pain that extends from the buttocks to the thighs, and if they continue unrelieved, you need to seek medical treatment in a timely manner.