Branches of the lower lumbar and upper sacral spinal nerves exit the spine and form the sciatic nerve. Once formed, the sciatic nerve gives sensory supply to the skin of the buttocks, back of the thigh and all of the lower leg and foot, except for the inner side. In addition to pain sciatica can also produce numbness and tingling in these areas.
As the sciatic nerve also gives motor supply to many leg muscles, then muscle weakness may also be a seen with sciatica.
The referral pattern of the ligaments in the sacroiliac joint can cause sciatic like symptoms. This joint can be hypermobile; most commonly in pregnancy or following trauma Eg, fall on to the buttocks. Conversely the sacro-iliac joint can be hypo mobile; stuck in a biomechanically poor position often due to repeated postures or old injuries.
This causes irritation or compression of a spinal nerve root and produce sradicular pain that corresponds to the nerve root affected. It may also be associated with loss of reflexes, changes to pinwheel sensation or muscle weakness.
These are small joints located at the back of the spine. They can cause similar sciatica symptoms to disc prolapse, but it does not follow the distribution of a spinal nerve and is therefore called referred pain.
The sciatic nerve passes through (or in some cases in front of) the piriformis muscle, deep in the buttock. Spasm of the piriformis can produce sciatica symptoms.
The management of sciatica will differ according to what is causing the sciatica symptoms.