Arthritis Treatment: Nerve-Related Knee Pain and How to Treat It

One of the most perplexing problems a rheumatologist faces is making the diagnosis in a patient who presents with knee pain. There are multiple causes of knee pain including arthritis, bursitis, tendonitis, as well as a host of other conditions.

One very common problem that is often overlooked is knee pain occurring as a result of nerve-related pain.

There are three nerves that can be associated with knee pain. The first is the femoral nerve. This is a nerve that runs down the front of the thigh. While rarely a cause of knee pain per se, it can cause pain in the front of the thigh.

The second nerve that sometimes causes pain in the back of the knee is the sciatic nerve. Patients with degenerative arthritis or degenerative disc problems can develop pain that runs from the low back down the back of the leg. What is interesting is that sometimes a patient will have leg pain but no back pain.

The final nerve that can be associated with knee pain is the peroneal nerve. This is a branch of the sciatic nerve and runs along the outside of the leg. Where this nerve becomes an issue is in a patient with a knee replacement. While this situation doesn't occur now very often, in the earlier days of knee replacement surgery, women would sometimes receive knee replacement hardware meant for men.

These replacements would be a bit too large for the joint and what would occur is that the peroneal nerve that runs along the outside of the knee joint would get irritated.

When that happened the patient would have severe pain. The typical scenario is of a woman patient who continues to have knee pain after the joint replacement surgery. She goes to see the orthopedic surgeon who takes x-rays, puts the films up on the view box, and pronounces, "The knee replacement looks perfect!" And the patient would say, "But my knee still hurts..." And the orthopedic surgeon would shrug his shoulders and say, "I don't know why."

The treatment of nerve-related knee pain is dependent on making a correct diagnosis. Usually femoral and sciatic nerve root pain are spine related. So the treatment is aimed at relieving whatever is causing nerve root irritation in the low back.

Peroneal nerve related knee pain, if it's due to irritation from a knee replacement appliance, can be treated with ultrasound guided hydrodissection of the peroneal nerve. What this involves is using a small needle to inject a large amount of fluid in the nerve sheath and moving the peroneal nerve away from the appliance. This often affords long term relief.

In patients where peroneal nerve compression continues and gets worse, there is progressive numbness, tingling, and weakness in the leg. The diagnosis can be confirmed by electrical studies such as electromyography. Patients who don't respond to hydrodissection may require neurosurgical consultation.