Pain caused by sciatic nerve irritation typically manifests as tingling, numbness, or even electric shock sensations in the affected leg, which follow the path of the sciatic nerve. It often accompanies pain in the lower back, but not always. This pain may increase with sitting, prolonged standing, and with hip movement. When it is more significant, the pain sometimes feels like a burning sensation.
Irritation or inflammation of the sciatic nerve, known as sciatica, can be caused by irritation of a nerve root to the spine (by a bulging or herniated disc, osteoarthritis, degenerative changes, etc). It can also be caused by a structure in the leg that prevents the nerve from moving properly, such as the piriformis (also called pyramidal) muscle located in the buttock. When this muscle compresses the sciatic nerve, we then refer to it as piriformis syndrome (or pyramidal syndrome).
The muscles behind the thigh and calves can also cause sciatic nerve irritation.