Sending a Message about Back Pain
There's some new thinking going on among doctors and researchers about back pain. Doctors used to think back pain that went below the knee from a disc problem was always caused by pressure on the spinal nerve root. When the disc pushes out of its normal space, it can come up against the spinal nerve as it leaves the spinal cord.

This pain from an irritated nerve is called radicular pain. Radicular pain begins in the low back and spreads or "radiates" down to the buttock, hip, knee, and lower leg (below the knee).

A separate and different cause of pain is called referred pain. Referred back pain from disc disease occurs in the low back but is also present in the hip, buttock, thigh, or lower leg. It doesn't spread from place to place. It is usually present in one or more locations at the same time.

Several new studies now show that the disc itself can refer pain into the lower extremity. Pain below the knee can be from the disc or from pressure on the nerve. This is important information because different treatment may be needed. Treatment depends on the actual cause of the pain.

More studies are needed to help doctors understand the exact pathways of pain. Better tests are needed to diagnose the exact cause of back pain. Studies are also needed to show which treatment works best for each type of pain.
Conor W. O'Neill, MD, et al. Disc Stimulation and Patterns of Referred Pain. In Spine. December 15, 2002. Vol. 27. No. 24. Pp. 2776-2781.