Muscle pain is called myofascial pain. Pain in a muscle is caused by muscle strain. Muscles are sprained when they are placed under excessive physical load. The sprain usually does not affect the entire muscle. It usually affects 1-2 muscle fibers within the entire body of the muscle. The sprain causes rupture of a few muscle cells which cause pain and inflammation. The area of sprain will heal in 1-2 weeks. During the healing time it is possible to feel a taut band within the affected muscle. This is called an active trigger point. Most time the sprain heals and the pain and the trigger point go away. Sometimes the pain resolves and the trigger point remains. This is called a latent trigger point. A latent trigger point does not cause pain unless it is prodded, rolled on or stretched. A latent trigger point will make the muscle more prone to injury.
Characteristics of active trigger points include:
- Sudden or gradual onset after muscle overload
- Referred pain (see below) characteristic of that muscle
- Weakness and restricted range of muscle
- A taut palpable band within the muscle
- Tenderness to pressure
- A twitch response in the muscle when snapping the trigger point with a
finger or needling
- Reproduction of the patient’s local and referred pain on examination and
during injection treatment
- Resolution of the pain with specific treatment of the trigger point.
The above diagram shows 2 (there are many other) trigger points in the neck that can refer pain to the head, face and jaw. Trigger points in the neck muscle are marked with an “X” and the areas of referred pain are marked in red.
As you can see, pain in the neck and shoulders can cause pain that appears to be coming from the jaw. When a patient presents to our office with a headache, or pain that can be felt in the TMJ (jaw joint) or jaw muscles, we have to determine how much (if any) of the pain) is related to the jaw and how much (if any) is related to trigger points in the neck and shoulders.