Fibromyalgia is a chronic condition causing pain in muscles, ligaments and tendons, as well as fatigue and multiple tender points, that affects an estimated 5 million Americans age 18 and older. The slightest pressure on tender points such as the neck, back, shoulders and hips can cause people with fibromyalgia to feel pain. Fibromyalgia is often considered an arthritis-related condition, but it is not truly a form of arthritis because it does not cause inflammation or damage to joints or muscles.
http://www.reporternews.com/news/2009/mar/25/understanding-and-living-fibromyalgia/