Numbness and pain in the left leg root may be caused by nerve compression and vascular diseases. 1. Nerve compression: the left leg root area belongs to the sciatic nerve travel area, the sciatic nerve by the compression or pulling stimulation, numbness and pain may occur, common diseases such as pear-shaped muscle syndrome, hip impingement syndrome, etc.; spinal nerves in the vertebral canal is compressed or damaged, may also appear below the innervation area of sensory abnormalities, such as lumbar disc herniation, lumbar spondylolisthesis, intradural tumors and so on. 2. Vascular diseases: the left leg root part belongs to the hip joint, when the blood vessels supplying the hip joint area are diseased, it will lead to the slowing down of the local blood, and the manifestation of tissue ischemia and hypoxia, such as arterial vascular occlusion of the lower limb, arterial stenosis of the lower limb, and so on, and the other vascular lesions caused by the left side of the femoral head necrosis, it is also possible to have the symptom of numbness and pain of the left leg root. If the symptoms of left leg root numbness and pain are not relieved, or accompanied by other symptoms, you should go to the hospital in a timely manner to consult the doctor and give targeted treatment after clarifying the cause.