Trigger point injections are used to relieve extremely painful areas of muscle.  Trigger points are very tight bands or small areas of a muscle that are very sensitive to touch and pressure.  The trigger point can irritate surrounding nerves and cause referred pain.  Referred pain is a type of pain that radiates to nearby areas.  Traumatic injury, overexertion, muscle tension, muscle spasms, pinched spinal nerves, and hormonal deficiencies are common causes of trigger points.  Trigger point injections are used to treat involved muscles in many areas of the body.  The neck, back and shoulders are particularly common areas injected.