This condition may be caused by three reasons: 1. It may be lumbar transverse process syndrome. Because the lumbar three transverse processes of aseptic inflammation, affecting the lumbar three of the nerve root, which leads to the buttocks and thighs of the anterior or lateral nerve pulling pain. 2, may be caused by lumbar intervertebral disc herniation. The lumbar disc herniation to the left side compresses the nerve root, which will lead to the left side of the buttock and the back of the thigh, nerve pulling pain. 3, caused by the pear-shaped muscle syndrome. Piriformis muscle is located in the middle of the buttocks, usually accompanied by the buttocks muscle is very obvious pressure pain, and the swelling of the piriformis muscle, will affect the sciatic nerve through the middle of the piriformis muscle, thus compression of the nerve leading to thigh pain. If you want to make a clear diagnosis, it is best to find a specialist to check it out, and do a CT or MRI of the lumbar spine to confirm the diagnosis if necessary.