What’s the difference between a nerve block and nerve degeneration? I have chronic sacroiliac joint pain, and I see on the Internet that both of these methods can work to stop the pain. But I can’t tell by reading the reports what’s the difference?

Nerves that innervate or tell a muscle or joint what to do can be divided into two types: sensory or motor. Sensory nerves conduct messages to the brain to tell it what’s going on in the muscle or the joint. Is there pain or a change in the position or pressure within the area? The sensory nerve picks up information from sensitive receptors and relays it to the brain. Pain is a common message carried by sensory nerves.

The motor branch of a nerve is responsible for taking messages from the brain to the joint or muscle and using that information to tell the structures to move. In the case of a nerve block, a numbing agent like novacaine (usually lidocaine is used) is injected into the joint. This local anesthetic blocks messages from the sensory nerve to the brain. It is one way to effectively cut off pain generated from that area.

Nerve blocks are temporary. In other words, like novacaine used in the dentist’s office to numb your gums, the numbing effects don’t last. Once the nerve block wears off, there is a chance the pain will still be there. But usually, in the case of something like chronic sacroiliac joint pain, the pain cycle has been broken and the pain is gone.

Sometimes, it takes two injections to get the full benefit. When those two injections are helpful but don’t provide complete (or strong enough) relief, then it may be necessary to cut the sensory nerve. Cutting the nerve is called denervation. The nerve will eventually grow back, but at such a slow pace, the original pain message will be long forgotten.

Motor nerves are not usually blocked or cut. They do not relay pain messages and disrupting these nerves will alter movement and function.