Tuesday, August 18, 2015

Trigger Points: A Common Cause of Musculoskeletal Pain

In upcoming blog posts I am going to describe common trigger points (often abbreviated as TrPs), discuss their clinical presentation (when it hurts, during which movements, how patients describe the pain, etc.) and pain patterns (where the pain refers to and is experienced by the patient). My goal is to educate patients on common pain patterns and give a few tips on how to prevent and alleviate this pain.

A trigger point is defined by Drs. Janet Travell, M.D., and David Simons, M.D., as a hyperirritable spot in a skeletal muscle that is associated with a hypersensitive palpable nodule in a taut band (a “taut band” is a tight area in a muscle). The spot is painful on compression and can give rise to characteristic referred pain, referred tenderness, motor dysfunction, and autonomic phenomena. This definition is from their excellent two-volume book Myofascial Pain and Dysfunction: The Trigger Point Manual.
Fig.1 Strumming across the fibers of a muscle
to feel taut bands and following it to locate
the TrP. From Travell and Simon's,
Myofascial Pain and Dysfunction

What this definition states is that a TrP in a muscle will be associated with a taut band within this muscle. If TrPs are present in a muscle and you or a practitioner strums across the fiber direction of that muscle, there will be a taut, ropy band that is present. Somewhere within this taut band, usually towards the central belly of the muscle, there will be a palpable nodule which is often exquisitely tender, especially with pressure applied (Fig.1). Usually a minimal amount of pressure will elicit this discomfort, if indeed it is not actively painful with no pressure. In fact, it might be this active pain that brings a patient in for evaluation.

The interesting thing about TrPs is that they have characteristic referral patterns which are where the patient experiences the pain (Fig. 2), either with pressure on the TrP, or, when very active, without. While this pain is sometimes in the vicinity of the TrP, many times it can be quite a distance away. This makes assessment and diagnosis somewhat tricky.
Fig.2 Gluteus Minimus TrP referral pattern which mimics
pain from neural compression causing sciatica.
This is sometimes referred to as pseudosciatica
Motor dysfunction caused by trigger points often involves how this muscle relates to its opposing muscle group (agonist-antagonist). Many times, the presence of TrPs can cause a muscle to become inhibited and it will not be able to perform its job effectively. This might be the case when this muscle, along with certain movements, also helps stabilize a joint.

The last part of the definition refers to autonomic dysfunction. Some TrPs can cause sweating, goosebumps, they can contribute to digestive disturbances, and can even contribute to positional vertigo.

It is important to note that TrPs appear as a result of muscle dysfunction and are not a precise anatomical aspect of a muscle. What I mean by this is that in a healthy muscle, there will be no signs of TrPs. When a muscle is overloaded due to repetitive use, injury, postural tension, stress, and other reasons, TrPs can form. Many times these TrPs can then become a chronic cause of pain.

Finally, while TrPs are very common, there are many other sources of orthopedic pain which can also refer. Spinal nerve impingement, vertebral joint syndromes, tendinopathies and many other conditions need to be taken into account whenever evaluating pain experienced by a patient.

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