Myofascial pain (MP) is a common, painful disorder that is responsible for many pain clinic visits. MP can affect any skeletal muscles in the body. Skeletal muscle accounts for approximately 50% of body weight, and there are approximately 400 muscles in the body. MP is responsible for many cases of chronic musculoskeletal pain and the diagnosis is commonly missed.
MP can cause local or referred pain, tightness, tenderness, popping and clicking, stiffness and limitation of movement, autonomic phenomena, local twitch response (LTR) in the affected muscle, and muscle weakness without atrophy. Trigger points (TrPs), which cause referred pain in characteristic areas for specific muscles; restricted range of motion (ROM); and a visible or palpable LTR to local stimulation are classic signs of MP. Over 70% of TrPs correspond to acupuncture points used to treat pain.
An active TrP is an area that refers pain to a remote area in a defined pattern when local stimulation is applied. Satellite TrPs appear in response to a primary, active TrP and usually disappear after the primary TrP has been inactivated. Latent TrPs cause stiffness and limitation of ROM but no pain. Frequently, they are found in asymptomatic individuals.
Although MP and fibromyalgia have some overlapping features, they are separate entities; fibromyalgia is a widespread pain problem, not a regional condition caused by specific TrPs.