Practitioners do not agree on what constitutes a<unk><unk> , but the assessment typically considers symptoms, pain patterns and manual palpation. Usually there is a taut band in muscles containing<unk><unk> s, and a hard nodule can be felt. Often a twitch response can be felt in the muscle by running your finger perpendicular to the muscle's direction; this twitch response often activates the "all or nothing" response in a muscle that causes it to contract. Pressing on an affected muscle can often refer pain. Clusters of<unk><unk> s are not uncommon in some of the larger muscles, such as the gluteus group (gluteus maximus, gluteus medius, and gluteus minimus). Often there is a heat differential in the local area of a<unk><unk> . A 2007 review of diagnostic criteria used in studies of<unk><unk> s concluded that : "there is as yet limited consensus on case definition in respect of MTrP pain syndrome. Further research is needed to test the reliability and validity of diagnostic criteria. Until reliable diagnostic criteria have been established, there is a need for greater transparency in research papers on how a case of MTrP pain syndrome is defined, and claims for effective interventions in treating the condition should be viewed with caution." A 2009 review of nine studies examining the reliability of<unk><unk>  diagnosis found that physical examination could not be recommended as reliable for the diagnosis of<unk><unk> s. Imaging Since the early 2000s several research studies have been conducted to determine if there was a way to visualize<unk> s using tools such as ultrasound imaging and magnetic resonance elastography. Several of these studies have been dismissed under meta-analysis. Another synthetic literature review expressed more optimism about the validity of imaging for<unk> s, but admitted small sample sizes of the reviewed studies.<unk>  pain syndrome<unk>  pain syndrome is a focal hyperirritability in muscle that can strongly modulate central nervous system functions. Scholars distinguish this from fibromyalgia, which is characterized by widespread pain and tenderness and is described as a central augmentation of nociception giving rise to deep tissue tenderness that includes muscles.<unk>  pain is associated with muscle tenderness that arises from<unk><unk> s, focal<unk> s of tenderness, a few millimeters in diameter, found at multiple sites in a muscle and the fascia of muscle tissue. Biopsy tests found that<unk><unk> s were hyperirritable and electrically active muscle spindles in general muscle tissue. Misdiagnosis of pain The misdiagnosis of pain is the most important issue taken up by Travell and Simons. Referred pain from<unk><unk> s mimics the symptoms of a very long list of common maladies, but physicians, in weighing all the possible causes for a given condition, rarely consider a<unk>  source. The study of<unk><unk> s has not historically been part of medical education. Travell and Simons hold that most of the common everyday pain is caused by<unk> s and that ignorance of that basic concept could inevitably lead to false diagnoses and the ultimate failure to deal effectively with pain.
Myofascial trigger point
Psychogenic pain
Calpainopathy
Phantom pain
Neurogenic claudication
Nerve compression syndrome
Peroneal strike
Myofascial pain syndrome