Pain in the lower back and hip radiating down the back of the thigh into the leg. The pain usually increases with flexion at the hip. Patients also experience numbness and occasionally weakness in the leg. The disorder can be caused by irritation of the sciatic nerve (irritants may be released from a ruptured disc in the back), by a pulled muscle injury, or by a bulging (herniated) lumbar disk compressing a nerve root, most commonly the L5 or S1 root.