Myofascial trigger point is a sensitive spot in a palpable taut band of skeletal muscle fibers. Two important clinical characteristics of trigger points, referred pain and local twitch response, can be elicited by mechanical stimulation (palpation or needling). The trigger point is usually activated by acute or chronic injury to a muscle, tendon, ligament, joint, disc or nerve. Recent human and animal studies have suggested that the pathogenesis of either referred pain or local twitch response is related to integration in the spinal cord. It has been proposed that there are multiple sensitive loci in a trigger point region. A sensitive locus may contain one or more sensitized nociceptive nerve endings. Mechanical stimulation of a sensitive locus can elicit a local twitch response which is frequently associated with characteristic referred pain. Theoretically, sensitive loci can be found in any site of a skeletal muscle, but is usually distributed with highest concentration near the endplate region where a trigger point is frequently found. The trigger point is a common pathogenic pathway of muscle pain from different causes.