Myofascial pain syndromes
Myofascial pain syndromes encompass a spectrum of disorders characterized by soft tissue pain with pain invoked by pressure at specific, repeatable, multiple points on the body. The most common associated diagnoses are fibromyalgia and myofascial trigger points. A distinction exists between "tender point" and "trigger point", but the two terms are often interchanged. Repeatable pain caused by palpation alone suffices to characterize tender points, along with other diagnostic criteria for fibromyalgia. The term regional soft tissue pain encompasses both " pain and localized tenderness not only in muscle but also in other contiguous soft tissues, such as ligaments and tendons" "Chronic widespread pain" is also used when there are multiple such points.
"Tender points" are the preferred term in fibromyalgia, the diagnosis of which, by the 1990 criteria of the American College of Rheumatology, included demonstrating pain on pressure in at least 11 of 18 paired tender points throughout the body.
Myofascial trigger point
Trigger points also produce pain on pressure, but they are also palpable as "knots" or "bunched" muscle tissue, "2 mm to 5 mm in diameter and tight bands that are painful when palpated." They are associated with trauma, while tender points are more indicative of diffuse or central disease. Causative trauma may be repetitive and subtle, such as trigger points in the neck being caused by frequent cradling of a telephone between head and neck. 
- Joanne Borg-Stein, MD (2006), "Treatment of Fibromyalgia, Myofascial Pain, and Related Disorders", Phys Med Rehabil Clin N Am 17: 491–510
- Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, et al. (1990), "The American College of Rheumatology 1990 criteria for the classification of fibromyalgia: report of the multicenter criteria committee.", Arthritis Rheum 33: 160-172
- Jack E. Hubbard (May 2010), "Myofascial Trigger Points: What Physicians Should Know about these Neurological Imitators", Minnesota Medicine