The trigger point model states that unexplained pain frequently radiates from these points of local tenderness to broader areas, sometimes distant from the trigger point itself. Practitioners claim to have identified reliable referred pain patterns which associate pain in one location with trigger points elsewhere. There is variation in the methodology for diagnois of trigger points and a dearth of theory to explain how they arise and why they produce specific patterns of referred pain.
Compression of a trigger point may elicit local tenderness, referred pain or local twitch response. The local twitch response is not the same as a muscle spasm. This is because a muscle spasm refers to the entire muscle contracting whereas the local twitch response also refers to the entire muscle but only involves a small twitch, no contraction.
Among MDs, many specialists are well versed in trigger point diagnosis and therapy. These include physiatrists (physicians specializing in physical medicine and rehabilitation), family medicine, and orthopedics. Osteopathic as well as chiropractic schools also include trigger points in their training. Other health professionals, such as occupational therapists, physiotherapists, acupuncturists, massage therapists and structural integrators are also aware of these ideas and many of them make use of trigger points in their clinical work as well,