Low back pain is pain in the region of the back between the bottom of the ribcage and the lower buttocks.
Sometimes the pain extends as far as the buttocks, into the back of the thigh and the outer calf, or into the groin. The muscles are in spasm and the back is stiff. In acute pain, the back is often tipped forwards and to the side. Sometimes low back pain is accompanied by a sharp, stabbing or prickling feeling in the back or buttocks.
If the pain comes on suddenly and unexpectedly, it is known as lumbago. If the pain lasts for longer than three months, it is referred to as chronic low back pain.