Trigger points are described as “hyperirritable spots of skeletal muscle associated with hypersensitive palpable nodules in a taut band" (Simons, 1999).
These points are commonly found in orthopedic conditions including headaches, neck and back pain, elbow pain, jaw pain and osteoarthritis.
These nodules are thought to develop due to altered electrical activity at the junction between nerves and muscle. These changes are sustained by changes in acetylcholine action, removal, and receptor activity.
Authors also note altered biochemical markers at the site of the trigger point including pH changes and markers involved in the nociceptive process.
These painful areas can either initiate or continue a pain response due to injury.
Myofascial Pain Syndrome, recognized by the American Pain Society, is hallmarked by the presence of trigger points in skeletal muscle. Authors have noted this is the most commonly overlooked diagnosis in chronic pain.