Pressure On The Nerve
Nerve damage to a leg can occur in various ways. You may injure a nerve directly through trauma, such as in an accident or maybe while participating in sports; or one of the discs that act as cushions between your spinal vertebrae may bulge out and put pressure on the sensory fibers of the nerve that branches out from the spine at that site. When this happens, the nerve sends a signal to the brain, which interprets these signals as pain.
Pain from pressure on a nerve may be localized, such as when you tear a ligament in your knee. It can also be referred---or transferred to---an area that is farther away from the spine, such as the leg pain that often accompanies a ruptured disc. This is often called radiculopathy. The path of the sensory changes will usually tell the doctor where the damaged originated. So, for example, if the pain travels down the back of your leg and into the calf, it may be due to sciatica, which results from a disc bulge in the lowest part of your lumbar spine.
Other Causes
Leg pain also may occur if you have a condition that limits blood and oxygen flow to the nerve. If this happens, nerve function is weakened, so its ability to transmit sensation is negatively impacted, usually starting at the part of the nerve that is farthest away from the spine, the hands and feet. These sensory changes may include tingling or numbness, but the leg or foot is frequently hypersensitive to touch and becomes more painful as the nerve damage progresses.
Diseases and Conditions
The main conditions that cause leg pain due to nerve damage are herniated lumbar spine discs and diabetes---especially if you've had it for a long time. In diabetes, this condition is called diabetic neuropathy. Other conditions where nerve damage might lead to leg pain are peripheral artery disease, alcoholism and vitamin deficiencies, some cancers, some kinds of autoimmune diseases, toxins, or even repetitive stress injuries, which can lead to nerve entrapment, though this is more common in the arms.
