The term Sciatica describes the symptoms of leg pain—and possibly tingling, numbness, or weakness—that originate in the lower back and travel through the buttock and down the large sciatic nerve in the back of each leg.
The sciatic nerve is the largest single nerve in the body and is made up of individual nerve roots that start by branching out from the spine in the lower back and then combine to form the "sciatic nerve." Sciatica symptoms occur when the large sciatic nerve is irritated or compressed at or near its point of origin.
The sciatic nerve starts in the lower back, typically at lumbar segment 3 (L3).
At each level of the lower spine a nerve root exits from the inside of the spinal canal, and each of these respective nerve roots then come together to form the large sciatic nerve.
The sciatic nerve runs from the lower back, through the buttock, and down the back of each leg.
Portions of the sciatic nerve then branch out in each leg to innervate certain parts of the leg—the thigh, calf, foot, and toes.
Sciatica is often characterized by one or more of the following symptoms:
Constant pain in only one side of the buttock or leg (rarely in both legs)
Pain that is worse when sitting
Leg pain that is often described as burning, tingling, or searing (versus a dull ache)
Weakness, numbness, or difficulty moving the leg, foot, and/or toes
A sharp pain that may make it difficult to stand up or walk
Pain that radiates down the leg and possibly into the foot and toes (it rarely occurs only in the foot)
Sciatic pain can vary from infrequent and irritating to constant and incapacitating. Symptoms are usually based on the location of the pinched nerve.