What is Myofascial Pain Syndrome?
Myofascial pain syndrome (MPS) is a chronic regional musculoskeletal pain disorder characterized by the presence of myofascial trigger points—hyperirritable, palpable nodules within taut bands of skeletal muscle or fascia that produce both localized and referred pain when compressed. 1, 2
Core Clinical Features
Trigger points are the pathognomonic finding: These are discrete, hypersensitive spots within muscle that feel like knots, nodules, or taut bands on palpation. 1, 3 When compressed, they reproduce the patient's pain either locally or in a characteristic referred pattern distant from the trigger point itself. 2, 4
Pain characteristics include:
- Deep, aching, or burning quality that may be constant or intermittent 5
- Regional distribution (not widespread like fibromyalgia) 2
- Referred pain patterns that follow predictable anatomical distributions 4, 6
- A local twitch response may occur when the trigger point is palpated 4
Epidemiology and Impact
MPS affects 30-93% of patients presenting to pain clinics, with an estimated lifetime prevalence of 85% in the general population. 4, 3 This wide prevalence range reflects the lack of standardized diagnostic criteria and frequent underdiagnosis due to symptom overlap with other musculoskeletal conditions. 1, 3
The condition significantly impacts quality of life, physical and social functioning, emotional well-being, and healthcare costs. 7
Pathophysiology and Risk Factors
The underlying mechanism involves sustained muscle contraction from overuse, underuse, or postural imbalance, though the exact pathophysiology remains incompletely understood. 2, 4
Contributing factors include:
- Acute trauma to muscles or fascia (including major injuries or minor procedures like dental work) 5
- Muscle overuse or repetitive strain 1
- Postural abnormalities and biomechanical dysfunction 1
- Psychological factors including stress, poor coping strategies, and depression 5
- Systemic conditions and comorbid chronic pain disorders 1, 7
Diagnostic Approach
Diagnosis is clinical, based on physical examination findings—there are no laboratory tests or imaging studies that confirm MPS. 2, 4 The general consensus for diagnostic criteria includes:
- Presence of at least one palpable trigger point within muscle or fascia 2, 4
- Pain upon palpation of the trigger point 4, 6
- Reproduction of the patient's familiar pain pattern (local or referred) 2, 6
- A local twitch response when the trigger point is stimulated 4
- Restricted range of motion in the affected muscle group 6
Manual palpation has good reliability for identifying trigger points, though some limitations are inherent to the subjective nature of the examination. 6
Critical Differential Diagnoses
MPS must be distinguished from fibromyalgia: MPS involves localized, regional pain with discrete trigger points, whereas fibromyalgia presents with diffuse, widespread pain and multiple tender points throughout the body. 2 However, these conditions commonly coexist. 2, 7
Other important differentials include:
- Neuropathic pain conditions (though MPS is primarily nociceptive, not neuropathic) 1, 8
- Joint disorders and arthropathies 1
- Rotator cuff pathology when shoulder is involved 9
- Giant cell arteritis in patients over 50 with facial/temporal pain 5
Pain Classification
MPS is primarily classified as a nociceptive pain condition driven by peripheral input from trigger points. 8 However, it can coexist with neuropathic or nociplastic pain phenotypes, particularly when associated with underlying medical conditions. 8 In such cases, the peripheral drive from trigger points should not be ignored, as treating them can reduce central sensitization symptoms. 8
Clinical Pitfalls
The condition is frequently underrecognized or misdiagnosed due to symptom overlap with other pain disorders and lack of standardized diagnostic criteria. 1, 3 Clinicians must maintain high clinical suspicion and perform careful manual examination of muscles for trigger points in patients presenting with regional musculoskeletal pain. 6
As MPS becomes chronic, it becomes increasingly refractory to treatment, emphasizing the importance of early recognition and intervention. 2