A trigger point injection can help soothe muscle pain, especially in your arms, legs, lower back and neck. It also can be used to treat fibromyalgia, tension headaches and myofascial pain. Trigger points are painful “knots” in your muscles. They form when a muscle can’t relax. Sometimes you feel these knots when you rub your muscle. Injecting small amounts of anesthetic and steroid into the trigger point can help alleviate the pain. Often a brief course of treatments will result in pain reduction.