Sciatica is the name that is often given to general back pain or pain that goes down the legs. However medically, it has a more precise meaning.
The sciatic nerve is a very large nerve that has several roots from the lower spinal cord. The nerves emerge from the lower spinal cord, and enter into the muscles in the lower back and pelvis. Here they all join together in a network of nerves called the lumbar plexus. From this plexus, the large sciatica nerve emerges and runs out of the pelvis and down the back of the leg.
The hole in the pelvis from which the sciatic nerve emerges from, is called the sciatic notch. This is just behind the hip joint and is deep below the buttock muscles. Not surprisingly then, people with sciatica find it very hard to sit down, as this puts pressure directly on the sciatic nerve as it runs out of the pelvis and into the leg.
If the sciatic nerve is pinched or irritated at all, the brain interprets this as pain along the course of the nerve - in other words from the lower spine on one side or other, running down through the buttock and into the back of the leg - often running past the hamstrings and down into the calf and heel.
True sciatica not only follows this pain distribution but also is worsened by stretching the sciatic nerve. This is tested for by doctors by either getting a patient to bend forwards with straight legs, which stretches the sciatic nerve as it runs deep to the buttocks, or by getting the patient to lie down and then lift the leg straight, bending the foot and toes towards the head. With sciatica, there is usually very little movement at the hip as this causes too much pain.
Sciatica is usually cured by bed rest on a hard bed or floor, painkillers and often muscle relaxants - to stop the muscle spasm which is a major cause of the pain. Occasionally if it does not improve, other interventions or surgery may be considered.