A trigger point is a knot or tight, ropy band of muscle that forms when muscle fails to relax. the trigger point can trap or irritate surrounding nerves and cause referred pain (pain felt in another part of the body.)

The injection is limited to what is called the "soft tissue" of the body. It is not given into the blood vessel, nerve, joint or the spinal canal.

Under local anesthetic, the pain medicine or (anti-inflammatory or steroid) is then injected into the appropriate area.

Injection of medication inactivates the trigger point and thus alleviates pain. Sustained relief usually is achieved with a brief course of treatment. Several sites may be injected in one visit.