Why is pain sometimes referred - in other words, if my back is injured, why do I feel pain in my thigh?
Referred pain is something that can occur in most parts of the body. A good example is if someone is having a heart attack. The pain can refer to the left arm, jaw, even the back.

With lower back pain, the injury can be around the waist level - for example - but the actual pain felt along the sciatic nerve and down the leg. This happens when the damaged part of the back presses on the nerve and the nerve relays the pain further down.