The lower extremities are innervated by spinal nerves that come from the lumbar and sacral region of the vertebral spine. Every spinal nerve divides into two roots as it leaves the spinal cord. The spinal nerve therefore divides into an "anterior root" and a "posterior root". The roots reunite into a common spinal nerve that exits the spinal column via the inter-vertebral foramina. Anterior roots contain motor nerve fibers that innervate muscles, causing them to contract. Posterior roots contain sensitive fibers that bring information from the body (in this case, the leg) to the central nervous system about pain, touch, and temperature. Pressure on the anterior spinal roots can cause motor symptoms such as muscle weakness or even paralyses. Pressure on the posterior roots can cause sensitive symptoms such as: itching, false sensations, and numbness. According to the localization of the symptoms you describe, your doctor can estimate which spinal nerve(s) is/are damaged. By removing the herniated disc, further nerve damage can be possible eliminated at that location...but the nerves that have been already damaged can’t be repaired completely so there are always some residual symptoms.