Occasionally, a specific muscle may generate pain due to sustained contraction and subsequent localized ischemia. While this type of pain is usually secondary to another problem, it can occur primarily. These areas of muscle pain are called trigger points and can be treated with injection of small amounts of local anesthetic solution with or without a steroid, usually in concert with specific physical therapy treatments. If the primary source of the muscle pain, such as an arthritic zygapophysial joint, is identified, then it is important to treat this primary pain source as well. Trigger point injections are usually performed in the office. Some deep muscle injections, such as the piriformis and iliopsoas muscles, are performed under fluoroscopy.