Genicular Nerve Block for Knee Pain in St. Louis

The knee joint does not have one nerve. Feeling reaches it through several small branches called the genicular nerves. Three are targeted most often: the superior medial, superior lateral and inferior medial genicular nerves. They run in set spots against bone at the edges of the joint. That is why a needle under image guidance can reach them, with no open surgery.

The skin is numbed. Then, guided by fluoroscopy (live X-ray) or ultrasound, a fine needle is moved to each nerve target. A small amount of local anesthetic goes in at each spot. The procedure takes about twenty minutes. You stay awake, and you walk out the same day. The anesthetic works within minutes, so we ask you to test the knee before you leave.

The block answers a question that imaging cannot. Is the pain really coming from the joint surfaces? Or is it coming from somewhere else, like the hip or the low back, and showing up in the knee? Strong relief in the hours after the block confirms the genicular nerves carry the pain. That result is what qualifies you for genicular radiofrequency ablation, the longer-lasting treatment.

Who is it for? Most often, people with knee osteoarthritis that has not responded to injections or physical therapy. Also people who cannot have or do not want a knee replacement. And people with lasting knee pain after a replacement that is otherwise well placed. It is one of several diagnostic and therapeutic nerve blocks we do. It is the knee version of the hip joint injection approach.

The genicular nerves branch off larger nerves. The superior medial genicular nerve comes from the saphenous or tibial nerve. The superior lateral comes from the common peroneal, and the inferior medial from the tibial. Here is what makes them easy to target. At set points, each runs right against the periosteum (the thin lining of the bone). That is where the thigh bone shaft meets the bump on its inner or outer side (the epicondyle), and at the matching point on the tibia.

Bone is the landmark. Under fluoroscopy those spots are easy to see and find again. So the needle goes to a bony stop, not to a guess. Cadaver studies have sharpened these positions. They also showed the anatomy varies enough from person to person that guidance is a must. It also explains why three targets are standard. No single nerve carries the whole joint, and blocking just one would give an unclear result.

This block belongs to a group worth naming: it is a prognostic block. Its main job is not to ease pain for a few hours. Its job is to predict whether shutting down those nerves would help. That changes how you read the result. Say the block gives great relief for exactly as long as the anesthetic lasts. That is the ideal outcome, even though the pain comes back. It proves the nerves carry the signal.

It also sets the bar. The reference trial for genicular radiofrequency chose patients based on a positive block. So doing ablation on someone who did not respond means treating outside the group where the benefit was shown. A negative block is truly useful. It points us to the hip, the low back or the soft tissue around the knee before anything permanent is done.