Trigger point injection (TPI) is used to treat extremely painful areas of muscle. Normal muscle contracts and relaxes when it is active. A trigger point is a knot or tight, ropy band of muscle that forms when muscle fails to relax. The knot often can be felt under the skin and may twitch involuntarily when touched (called a jump sign).
The trigger point can trap or irritate surrounding nerves and cause referred pain — pain felt in another part of the body. Scar tissue, loss of range of motion, and weakness may develop over time.
TPI is used to alleviate myofascial pain syndrome (chronic pain involving tissue that surrounds muscle) that does not respond to other treatment, although there is some debate over its effectiveness. Many muscle groups, especially those in the arms, legs, lower back, and neck, are treated by this method. TPI also can be used to treat fibromyalgia and tension headaches.
Injections are given in the physician’s office or out-patient surgery center and takes approximately 15-30 minutes.
A small needle is inserted into the trigger point and a local anesthetic with or without a corticosteroid is injected. Injection of medication inactivates the trigger point and thus alleviates pain. Sustained relief usually is achieved with a brief course of treatment. The injection may cause a twitch or pain that lasts a few seconds to a few minutes.
Numbness from the anesthetic may last about an hour and a bruise may form at the injection site. Pain can be relieved by alternately applying moist heat and ice for a day or two. In most cases, stretching exercises and physical therapy are performed following TPI.
The patient should contact the physician if redness or swelling develops. There is a very rare risk for puncturing a lung or the membrane that surrounds the lung (called the pleura), when a muscle near the ribcage receives a trigger point injection.