Before turning to yoga, you should meet with a doctor to determine what's causing your sciatica. Sciatica is defined as pain caused by irritation or pressure anywhere along the sciatic nerve. The nerve extends from the sacrum, between layers of the deep buttock muscles, and then into the deep muscles of the back of the thigh.
Mary Pullig Schatz, M.D., offers the following information about sciatica in her book, Back Care Basics: A Doctor's Gentle Yoga Program for Back and Neck Pain Relief:
"Characteristically, this pain starts in the buttock and extends down the rear of the thigh and lower leg to the sole of the foot, and along the outer side of the lower leg to the top of the foot. Pain may also be felt in the lower back.
"A primary cause of sciatica is a herniated or bulging lower lumbar intervertebral disc that compresses one of the nerve roots before it joins the sciatic nerve. Sometimes irritation of a branch of the sciatic nerve in the leg can be so severe as to set up a reflex pain reaction involving the entire length of the nerve. For example, if the nerve is pinched or irritated near the knee, you may feel the pain in the hip and buttock.
"Another cause of sciatica is piriformis syndrome. The piriformis muscle extends from the side of the sacrum to the top of the thigh bone at the hip joint, passing over the sciatic nerve en route. When a short or tight piriformis is stretched, it can compress and irritate the sciatic nerve. People who habitually stand with their toes turned out often develop piriformis syndrome, as do runners and cyclists, who overuse and understretch the piriformis muscle.
"In order to work therapeutically with sciatica, you must deal with its basic cause." Regularly performing sets of certain asanas can help to relieve some types of sciatic pain. Here are some suggestions from Schatz.
If the sciatica is from a bulging disc, focus on improving posture and body mechanics in daily activities. Yoga practice should be modified so that the pain is neither created nor intensified. Good poses to work with are Tadasana (Mountain Pose), Adho Mukha Svanasana (Downward-Facing Dog) and its modification, Push the Wall Pose, as well as Virabhadrasana II (Warrior II Pose). Do several sets, holding each pose for a moment.
If a tight piriformis muscle is the problem, then it must be gently stretched. Schatz suggests Piriformis Stretch, a seated pose that resembles the leg position of Matsyendrasana (Lord of the Fishes Pose), but without the torso twist. Parivrtta Trikonasana (Revolved Triangle Pose) with the support of a table or countertop can also help. Do not overstretch or more spasm can result. These poses can help relieve both piriformis spasm and piriformis-related sciatica. Remember to always speak with a physician before beginning any type of physical exercise.