Sciatic nerve is the nerve originating in the lower spine as nerve roots exit the spinal cord and extends all the way down the back of the leg to the toes. The sciatic nerve is a combination of the fourth and fifth lumbar nerves (L4 and L5) and the first three nerves in the sacral spine (S1-S3). The sciatic nerve supplies sensation and strength to the leg as well as the reflexes of the leg. It connects the spinal cord with the outside of the thigh, the hamstring muscles in the back of the thighs, and muscles in the lower leg and feet. When the sciatic nerve is irritated or inflamed, it can lead to muscle weakness in the leg and/or numbness or tingling and cause sciatic nerve pain or sciatica.