Trigger point injections, or TPI, are another pain relief option. TPI is used to treat areas of muscle that are causing pain due to unrelaxed muscles containing trigger points, which result in knots of the muscle. These knots may cause referred pain, or pain that is felt in a body part in a location separate from the source of the issue. The referred pain is caused by irritation of the surrounding nerves. TPI is used to help alleviate the pain by inserting a small needle into the trigger point rendering it inactive. TPI can use a local anesthetic or saline, which may include corticosteroid. Another technique is dry needling, which involves no medication.