Fibromyalgia (FMS) is described as a painful body condition affecting the muscles but with many other symptoms. It's most likely a systemic problem. Researchers think it's caused by altered function of the nervous system in connection with hormones. The exact cause remains unknown.

Myofascial pain syndrome (MPS) is a local problem affecting the muscles. Overuse and repetitive motion are the main causes of MPS. Trigger points are described as overly irritable spots within a muscle. There's usually a taut band of tissue around the trigger point. The painful spots and painful muscles of these two conditions may be similar but the two overall conditions are very different.

It can be difficult to tell the difference between the tender points of FMS and the trigger points of MPS. Sometimes patients have both. Well-trained experts are often unable to identify which is which just by feeling or palpating the muscles.