The left side of the leg pain caused by lumbar disc herniation is mainly due to the following reasons: 1. The lumbar disc ruptures due to gradual degeneration, and the nucleus pulposus protrudes from the fibrous ring under gravitational pressure to compress the lumbar nerve roots on the left side. The left lumbar nerve root mainly innervates the left lower extremity, if it is compressed to the lumbar three lumbar four nerve root, it will lead to the lumbar four nerve root distribution area, such as the inner side of the calf appears obvious pain. 2, if the lumbar four lumbar five disc protrusion, it will compress the lumbar five nerve root, manifested as the outer side of the calf and five toes and the back of the foot appears obvious pain. 3, if the lumbar five sacral one disc protrusion, compression If the degree of compression is heavy, it will cause obvious radiating pain symptoms in the entire lower limb.