Sciatica is specifically nerve pain involving the posterior aspect of the thigh, calf or foot and which is caused by irritation or compression of  the sciatic nerve, the main nerve into the leg.  Pain may originate where the nerves pass through and emerge between the lower bones of the spine (lumbar vertebrae) or as the nerve passes through the Piriformis muscles in the pelvis.. There may be numbness and weakness of the lower leg muscles and loss of reflexes.

Sciatica and low back pain                                                    
Sciatica is often combined with low back pain. The order in which the symptoms appear may vary.  Back pain often precedes sciatica and sometimes will follow.

Causes and effects
The most common cause of true sciatica is a "slipped, prolapsed, twisted or bulging disc". The discs (or inter-vertebral discs) are the cushions which separate the bones of the spine (vertebrae).

Sciatica may cause  the sufferer to bend forward or sideways in an attempt to avoid further nerve compression (antalgia).

Treatment

Chiropractors perform chiropractic, orthopaedic and neurological tests and normally take lower-dose Digital Computerised X-Rays while the patient stands, so that major curvature and disc compression can be shown. The X-ray will also detect any congenital spinal deformities, bone cancer and osteoporosis (brittle bones).

Treatment may involve gentle and specific spinal mobilisation or manipulation, soft-tissue therapy, acupuncture, laser or ultrasound.

Chiropractic treatment is very effective in the vast majority of cases.

Where examination indicates a very large disc prolapse with major neurological symptoms and signs an MRI scan will be arranged and neurosurgical referral will be made without delay.