Pain in the buttock that radiates down the leg is commonly called sciatica. The most common cause for sciatica is irritation of the spinal nerves in or near the lumbar spine. Sometimes the nerve irritation is not in the spine, but further down the leg.one possible cause one possible cause of sciatica is piriformis syndrome.

Lower crossed syndrome (LCS) is a frequent muscular dysfunction syndrome, which may cause chronic low back pain due to muscular imbalance