Sciatica is the name given to any sort of pain that is caused by irritation or compression of the sciatic nerve – which runs down the back of your thigh into the back of the knee where it splits into two branches and descends into the lower leg and foot. Sciatic pain can vary widely, from mild, infrequent and irritating to severe, constant and debilitating. There are many different causes of sciatica. The most common ones are: bulging disc or disc degeneration spinal degene