Genicular Nerve Block for Knee Pain in St. Louis

The knee joint does not have one nerve; sensation 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 predictable positions against bone at the edges of the joint, which is what makes them reachable with a needle under image guidance rather than through open surgery.

The skin is numbed and, under fluoroscopic or ultrasound guidance, a fine needle is advanced to each nerve target. A small volume of local anesthetic is placed at each site. The procedure takes about twenty minutes, you remain awake, and you walk out the same day. Because the anesthetic acts within minutes, we ask you to test the knee before you leave.

The block answers a question that imaging cannot: is the pain actually coming from the joint surfaces, or from something else such as the hip or the lower back referring into the knee? Substantial relief in the hours after the block confirms the genicular nerves are carrying the pain, and that result is what qualifies you for genicular radiofrequency ablation, which is the longer-lasting treatment.

The common candidates are people with knee osteoarthritis who have not responded to injections or physical therapy, those who cannot have or do not want a knee replacement, and those with persistent knee pain after a replacement that is otherwise well-positioned. It is one of several diagnostic and therapeutic nerve blocks we perform, and the knee equivalent of the hip joint injection approach.

The genicular nerves are branches of larger trunks. The superior medial genicular nerve arises from the saphenous or tibial nerve, the superior lateral from the common peroneal, and the inferior medial from the tibial. What makes them targetable is that at specific points each runs directly against periosteum, at the junction between the femoral shaft and the medial or lateral epicondyle, and at the corresponding point on the tibia.

Bone is the landmark. Under fluoroscopy those junctions are visible and reproducible, so the needle is advanced to a bony endpoint rather than to an estimate. Cadaveric studies have refined these positions and shown the anatomy varies enough between individuals that guidance is not optional. It also explains why three targets are standard: no single nerve carries the whole joint, and blocking one would produce an ambiguous result.

This block belongs to a category worth naming: it is a prognostic block. Its purpose is not primarily to relieve pain for a few hours but to predict whether destroying conduction in those nerves would help. That reframes how the result should be read. A block that produces excellent relief for exactly the duration of the anesthetic is an ideal outcome, even though the pain returns, because it demonstrates the nerves carry the signal.

It also sets the threshold. Because the reference trial for genicular radiofrequency selected patients on the basis of a positive block, applying ablation to someone who did not respond means treating outside the population in which benefit was demonstrated. A negative block is genuinely useful information: it redirects attention to the hip, the lumbar spine or the soft tissue around the knee before anything irreversible is done.