Myofascial Pain Syndrome

Myofascial pain syndrome is pain that arises from muscles or related fascia and is characterised by the presence of myofascial trigger points (MTPs). 
==Definition==
Myofascial Pain: is pain that arises from muscles or related fascia.
Myofascial trigger point: A palpable hypersensitive tender nodule in a taut skeletal muscle band with a twitch response. Pressure can also cause a characterised referred pain pattern, motor dysfunction, and autonomic responses (e.g. vasodilation, vasoconstriction, piloerection).
A MTP can be latent or active. 
*Active MTPs: Spontaneously painful with increased pain on contraction or stretching of the muscle
*Latent MTPs: Focal tender and tight areas that aren't spontaneously painful but may restrict range of motion and strength
==Pathophysiology==
The pathophysiology isn't completely known and is controversial. The MTP is associated with endplate noise from a motor endplate that releases abnormal amounts of acetylcholine. Sarcomeres are shortened in the endplate regions which cause a local release of sensitising substances resulting in pain.
They are often related to nociplastic pain and allodynia/hyperalgesia.
==Aetiology==
*Acute muscle overload
*Repetitive stress or prolonged abnormal postures
*Radiculopathy
*Trauma
*Other trigger points
*Visceral pain
*Joint dysfunction
*Emotional distress
==Clinical Assessment==
===Clinical Features===
Palpation: The MTP should be palpated perpendicular to the direction of the muscle fibre. When palpating over a firm or bony structure compress the muscle against it. In some areas the muscle can be grasped between the fingers with a pincer grip to allow for MTP palpation. Referred pain is most readily detected with palpation in the centre of the MTP. So move your fingers along the taut band to find the hardest and most tender spot. 
Referred Pain: When found compress it for 5-10 seconds and ask the patient if there is local or referred pain. Referred pain is somewhat follows the myotome pattern of innervation. For example, infraspinatus is primarily innervated by C5, and tends to refer pain to other C5-innervated muscles, with also a spread to C4 and C6 muscles (Also see Deep Somatic Pain).
Twitch Response: A local twitch response can occur which is when pressure over the MTP causes localised contraction. It is a brief (25-250ms), high-amplitude, polyphasic electrical discharge. It is dependent on an intact spinal cord reflex arc. It isn't seen in healthy muscle.Gerwin RD. Diagnosis of myofascial pain syndrome. Phys Med Rehabil Clin N Am. 2014 May;25(2):341-55. doi: 10.1016/j.pmr.2014.01.011. Epub 2014 Mar 18. PMID: 24787337.
Weakness and ROM Restriction: There may be increased tension and shortening with restricted range of motion and weakness with poor muscle activation patterns. MTPs typically occur in muscles that are fatigued, overloaded, weak, or activated because of failure of other muscles. Weakness can be temporarily reversed with inactivation of the trigger point.
Autonomic Changes: There can be vasodilation or vasoconstriction due to autonomic nervous system activation. This can be seen as erythema or blanching.
===Clinical Syndromes===
In a myofascial pain syndrome there may be just one trigger point but more typically there are several trigger points.
Area 	Involved Muscles
Low back Pain 	
*Quadratus lumborum: low back with radiation into the legs or testicles
*Iliopsoas: vertical band in low back and upper anterior thigh
*Gluteus medius: sacral and buttock area and lateral hip
Neck and Shoulder Pain 	
*Trapezius: upper trapezius refers pain to the back of the neck and angle of the jaw
*Levator scapula: angle of the neck and shoulder
Hip Pain 	
*Gluteus medius
*Gluteus minimus
Pelvic Pain 	
*Levator ani
Headaches 	
*Sternocleidomastoid: anterior face and supraorbital area
*Upper trapezius: vertex of the forehead and temple
*Deep cervical muscles: post-occipital and retro-orbital pain
Jaw Pain 	
*Masseters and Pterygoids
*Upper trapezius and sternocleidomastoid
Upper Limb Pain 	
*Subscapularis
*Infraspinatus
*Teres Major
*Serratuis Anterior
*Pectoralis minor: radiating pain down the ulnar side of the arm into the little finger.
Lower Limb Pain 	
*Tensor fascia lata: lateral thigh pain
*Iliotibial band: lateral knee pain
*Quradriceps: anterior knee pain
*Hamstring and popliteus: posterior knee pain
*Anterior tibialis: anterior leg pain
*Peroneus longus: lateral ankle pain
Chest and Abdominal Pain	NB: MTPs can accompany true visceral pathology (see Visceral Pain)
*Pectoralis major: ipsilateral anterior chest pain with radiation down the ulnar side of the arm
*Sternalis: deep substernal pain
*Rectus abdominis: abdominal pain
==Investigations==
Blood tests can include TSH, ferritin, vitamin D, and vitamin B12.
==Diagnosis==
The first three are essential for the diagnosis, the last five are not required.
#Taut band within the muscle
#Exquisite tenderness at a point on the taut band
#Reproduction of the patient’s pain
#Local twitch response
#Referred pain
#Weakness
#Restricted range of motion
#Autonomic signs: skin warmth or erythema, tearing, piloerection.
A pragmatic definition is the presence of a tender taut band that reproduces the patient's pain in full or in part.
==Differential Diagnosis==
Myofascial pain should be distinguished from fibromyalgia. Widespread myofascial pain can be confused with fibromyalgia but there are some important differences.
Myofascial Pain 	Fibromyalgia
No female preponderance 	Female preponderance (8:1)
Regional pain 	Widespread pain
Local tenderness 	Widespread tenderness
Hardy ropy muscles 	Soft doughy muscles
Reduced range of motion 	Hypermobility
Trigger points 	Tender points
Immediate response to trigger point injections	Delayed or poor response to trigger point injections
Myofascial pain can occur in conjunction with fibromyalgia as well. In some individuals the dysfunctional neuromuscular junctions may be the primary driver in the central sensitisation that is characteristic of fibromyalgia.
==Treatment==
===Posture and Ergonomics===
Correct any predisposing factors.
===Manual Therapy===
Manual therapy can be used to improve range of motion, but this may not necessarily improve pain.Guzmán-Pavón MJ, Cavero-Redondo I, Martínez-Vizcaíno V, Torres-Costoso AI, Reina-Gutiérrez S, Álvarez-Bueno C. Effect of Manual Therapy Interventions on Range of Motion Among Individuals with Myofascial Trigger Points: A Systematic Review and Meta-Analysis. Pain Med. 2022 Jan 3;23(1):137-143. doi: 10.1093/pm/pnab224. PMID: 34289061.
*Muscle energy techniques including Postisometric relaxation
*Ischaemic compression
*Stretching
*Strain-counterstrain technique
*Positional release technique
*Pressure release
*Transverse friction massage
*Joint manipulation
Treatment of an MTP depends on the cause
#Muscle is weak and fatigues quickly: treatment is strengthening
#Muscle is overactive and compensating for other muscles that aren't correctly activating: restore correct motor pattern for example scapula stabilisation
#Muscle is inappropriately active: modify inappropriate activities that are overloading the muscle e.g. holding one's phone between the head and shoulder.
===Trigger Point Injection===
The trigger point is peppered with lidocaine using a fine needle to inactivate the trigger point. The MTP is accurately located by finding a local twitch response with the needle tip. Some clinicians add dextrose to the local anaesthetic e.g. at a concentration of 5%.
===Medications===
Options are NSAIDs and tricyclic antidepressants.
==See Also==
*triggerpoints.net
*Central Sensitisation
*Allodynia and hyperalgesia
*Fibromyalgia
*Deep Somatic Pain
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==References==
Category:Widespread
Category:Functional Approaches