*Before we jump into it, Myofascial trigger point still needs investigations and research as to diagnostic criteria, reliability and even existence. Thus, we should avoid using this term to describe all musculoskeletal pain.
What is it?
Myofascial trigger points (MTrPs) refers to a hard, hyperirritable and taut band in the skeletal muscle that is painful with (active) or without (latent) compression [1, 2]. The presence of MTrPs can manifest muscle weakness, restricted ROM, pain and muscle dysfunction.
The current diagnostic criteria for MTrPs needs to meet 2 out of following 3: a taut band, a hypersensitive spot, referred pain and reproduction of similar pain character by stimulating MTrPs . Once this spot is found, the spot is compressed gently and a patient is asked if the pain feature is similar or not, if pain is referring anywhere and how tender it is. However, this criteria is subjective, inconsistent and not quantitative.
How could this be formed? -Integrated hypothesis-
The most known hypothesis is the integrated hypothesis of energy crisis at motor endplate and excessive noxious chemicals and neurotransmitters stimulating nociceptors.
When muscle contracts, Ca2+ comes out of sarcoplasmic reticulum and connects to troponin in the muscle fibres and ATP is required for Ca2+ getting back in to relax the muscle.
When action potential occurs, acetylcholine (ACh) is released in the synapse, binds to protein and moves to the presynaptic cleft, then the bound Ach is send to postsynaptic cleft to combine with receptors, resulting in Na+ going into cell followed by Ca2+ [1,11].
Better to watch videos than just read.
Myofascial pain syndrome (MPS)
Myofascial pain syndrome (MPS) is the term of localised pain considered to be caused by one or more MTrPs . When this term is used, other conditions must be ruled out. Otherwise, unexplained conditions could all be MPS. This is thought to be associated with fibromyalgia, rheumatic disease, tension type headache, carpal tunnel syndrome and pelvic pain .
I used to think a lot about this as I have studied the remedial massage and myotherapy, but the more I study, the less I use this term and the less time I think about this. (Yes, I do still have this in my head but not the first or second option. Of course, it depends on patients though). It may exist to provoke muscular related pain or dysfunction. This my though change will be explained next a few paragraphs.
Non-specific pain (BPS) vs MPS (pathoanatomic)
If we can find a reliable qualitative measure to identify MTrP, we may be able to say MPS dur to MTrP. If MTrP is seen any musculoskeletal conditions, MTrP cannot be a specific cause of MPS. For instance, if MTrPs seen in rotator cuff tendinopathy, groin pain in athlete and ACL injury, are they all MPS? If so, would you just do MTrPs on all the conditions? Imprecise objective measurement (palpation) makes diagnosis uncertain. MPS is an ambiguous term to describe musculoskeletal conditions and heavily focus on biomedical model [1,].
Non-specific pain is used when conditions or pain result from multiple factors, are challenging to diagnose, hard to label biomedical diagnosis and not improved by multiple interventions [4,6].
Pain science has gotten the huge attention recently and we all understand pain is complex.
Knowing and comprehending pain science and BPS model tells us that we need to look at psychological, social and environmental factors too.
An example of the diagnostic criteria for fibromyalgia
The classification criteria established in 1990 proposed that widespread pain with tenderness in 11 or more of the 18 fixed points was the diagnosis criteria . This criteria was scrutinized in 2010-2011 as a quarter of patients did not fit in the criteria and there was a shift from just chronic pain to multiple symptoms. Amended criteria for diagnosis of fibromyalgia made is the following: widespread pain, fatigue, sleep disturbance and somatic symptoms such as pain, weakness, fatigue and shortness of breath. Palpation was not in the criteria . Pain area 6 out of 9 sites (head, left arm, right arm, chest, abdomen, upper back and spine, lower back and spine including buttocks, left leg and right leg), sleeping issues and fatigue are set as a chief criteria.* Other symptoms and factors such as tenderness, cognitive problem, heridity and psychological factors can be considered but not required . Basically, the criteria has shift from tenderness (pathoanatomical) to multiple factors such as cognitive, psychological factors and somatic symptoms (BPS).
*19 regions of the body chart may be used .
Tenderness and central sensitization
Pain science is the biggest interest of mine but will go on for ages to talk about it so not mention in detail here.
When the nociceptor detects noxious stimuli (tissue damage, injury etc…), this information conveys to the brain via spinal cord in order to notice some danger or signs from the body. There are some mechanisms to modulate pain from spinal cord to the brain (not going to talk about this time). These are the normal reactions of the body. However, repetitive injuries, trauma, sleep problems and other psychological factors cause hyperactive central nervous system, which means that a body may detect non-noxious stimuli (allodynia) or low level of noxious information (hyperalgesia) as pain. This is called central sensitisation [12, 13]. On the other side, if you like pain (no pain no gain) or this information is modulated, we may not complain as pain but just discomfort.
I am pretty sure that everyone has experienced patients with high pain threshold, even in fibromyalgia patients. Someone can tolerate a deep and firm pressure but sensitive to dry needling or cupping. Or athletes who started receiving a firm treatment when they were young can tolerate pretty well? This may be because they are used to having a deep hands-on and the body does not find it painful information.
Like the example of fibromyalgia criteria, things change all the time. We should not stick with one concept but be flexible to new theories and question them.
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