To best understand the cause of your pain, spine specialists sometimes divide low back pain into two categories:
- mechanical pain
- neurogenic pain
Mechanical back pain is caused by wear and tear in the parts of the lumbar spine. This type of pain is similar in nature to a machine that begins to wear out. Mechanical pain usually starts from degenerative changes in the disc. As the disc begins to collapse and the space between the vertebrae narrows, the facet joints may become inflamed. Mechanical pain typically gets worse after activity due to strain on the moving parts of the spine. Mechanical pain is usually felt in the back, but it may spread into the buttocks, hips, and thighs. The pain rarely goes down past the knee. Mechanical back pain usually doesn’t cause weakness or numbness in the leg or foot, because the problem is not from pressure on the spinal nerves.
Neurogenic pain means pain from nerve injury. Neurogenic pain occurs when spinal nerves are inflamed, squeezed, or pinched. This can happen when a disc herniates or when a nerve gets pinched where it leaves the spine. Recently it has also become known that when a disc ruptures, chemicals are released that inflame the nerves even if there is no pressure directly on the nerve. Neurogenic symptoms concern doctors more than mechanical pain because they can signal damage to the nerves and lead to weakness or numbness in the lower extremities.
The nerve pressure causes symptoms in the areas where the nerve travels, rather than in the low back. This happens because pressure on the spinal nerve affects structures away from the spine, such as the muscles. As a result, a person’s back may not hurt, yet the person feels pain, numbness, or weakness in the leg or foot. This indicates there’s a problem with the body’s electrical wiring. The pressure on the nerve affects how the body functions. Muscles weaken. Reflexes slow. Sensations of pins, needles, and numbness may be felt where the nerve travels.