“Trigger points”, often referred to as “knots” or “tension points” in muscle tissue, are a commonly seen source of physical pain and/or dysfunction in patients. But what exactly is a trigger point, and why is their diagnosis and treatment important?
A trigger point is classified as “a hyper-irritable spot within a taut band of a skeletal muscle that is painful on compression, stretch, overload, or contraction in the shortened position, and responds with a referred pain pattern that is often distant from the spot” (Simmons et al., 1999).
These trigger points, essentially spots of unhealthy tissue contained within a taut band of tissue within the overall muscle, are responsible for the production of noxious (pain eliciting) chemicals, which nerve endings in the muscle relay to the spinal cord and subsequently the brain. Initially, upon initial transmission of these harmful stimuli, the brain has capacity to override or “dampen down” these signals, so pain is not actually guaranteed to be felt. This scenario becomes more troublesome as the brain becomes more used to and more efficient at relaying these pain signals however, and the brain’s ability to tone down these painful signals lessens over time also. Besides producing pain and harmful chemical signals, both active and passive trigger points can also cause muscular weakness, spasm, and incorrect recruitment patterns in muscle tissue in which they present.
Trigger points, are of clinical importance for several reasons. Primarily, trigger points can cause pain and other similar symptoms, and their presence can also interfere with normal muscular function. This essentially means that trigger points can directly act as the cause of symptoms, or can directly cause altered movement patterns or inefficient muscular usage, which can subsequently lead to the emergence of pain and symptoms over time.
Trigger points can be described as being either “active” or “latent”. Upon examination, when the application of moderate pressure to a trigger point evokes the patient’s familiar pain, this is regarded as an active trigger point ie. there is direct reproduction of actual symptoms upon stimulation of the trigger point. If symptoms are produced, but do not bear resemblance to the patient’s own, usual headache symptoms, this is deemed a latent trigger point ie. symptoms are produced, but these are not the symptoms which the patient has reported prior to the physical examination. Latent trigger points, while not an acute concern as they are not seen to be responsible for producing current pain, are worthy of attention nonetheless, due to their tendency to interfere with local muscular function and homeostasis.
Many factors can cause trigger points within muscle tissue – continued over-loading of a muscle lacking capacity for this level of loading, repeatedly placing the muscle in a position of prolonged lengthening, poor movement mechanics, and simple trauma are common causes. Restoration of normal muscle condition and function is sought to cease this flow of noxious stimuli from trigger points to the spinal cord. This is achieved through a combination of manual therapy, strengthening, and a rounded approach to lifestyle and ergonomic habits. In many cases, challenging (training!) the implicated muscle to improve its strength and endurance capacities will lead to a reduction in irritation, as the muscle becomes better conditioned to tolerate the load or challenge which is being placed upon it by lifestyle, ergonomic, or exercise factors.
Commonly seen trigger points include trigger points in the Infraspinatus (shoulder blade) muscle which can cause pain at the front of the shoulder, Upper Trapezius (muscle joining the neck & shoulder) muscle which can cause neck pain and headaches, and pain in the VMO (inside of the knee) muscle which can cause pain at the front of the knee.
Our physiotherapy staff are highly trained in identification and treatment is conditions which are underpinned by the presence of trigger points, and in treating and rehabilitating these conditions to resolution.
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