The nerves that transmit the sensation of pain to the legs and feet are located in the lower back region. Occasionally with age or injury, the discs between the vertebrae can bulge out and press on these nerves. When this occurs the nerve becomes irritated and sends out pain signals. The location of the pain depends on which disc is protruded. How bad the pain is depends on how much of the disc is pressing on the nerve.
The nerves that send fibers to the knee are located at the second, third, and fourth lumbar vertebral levels in the lower back area. If a disc is compressing on the nerves at these locations, the pain very may be felt in the knee region. This condition can be diagnosed by your physician with a thorough history and physical exam.
Treating this disorder can be accomplished with surgery, steroid injections, medications, or physical therapy. The conservative route is often favored initially.