The cause of fibromyalgia is not known, though many factors may contribute. These triggers include sleep disturbances, abnormal pain responses, and emotional or physical trauma. An infection may trigger or cause fibromyalgia, though no virus has been identified.
The pain experienced with fibromyalgia can range from mild to severe. Patients with fibromyalgia have especially painful areas called tender points, where they experience additional pain when they place firm pressure.
These tender points are located in the soft tissue of several areas of the body, including the knees, lower back, elbows, back of the neck, shoulders, shins, chest and hips.
Pain starts in the tender points then spreads out. While the joints are not affected in fibromyalgia, patients may feel as if the pain does come from there. Fibromyalgia pain may feel like burning or a deep ache.
Fibromyalgia may cause morning stiffness. Some patients with fibromyalgia experience pain all day.
https://www.empowher.com/fibromyalgia/content/symptoms-fibromyalgia