What is myofascial pain syndrome, its etiology, pathophysiology, clinical presentation, diagnostic criteria, and rehabilitation treatment?

Myofascial Pain Syndrome: Comprehensive Overview

Definition

Myofascial pain syndrome (MPS) is a chronic regional musculoskeletal pain disorder characterized by hyperirritable trigger points within taut bands of skeletal muscle fibers that produce both localized and referred pain. 1, 2 These trigger points are discrete areas of tenderness that, when palpated, recreate the patient's pain at the site or produce pain in a characteristic referral pattern away from the trigger point. 2

MPS affects up to 85% of adults during their lifetime and is distinct from fibromyalgia in that it involves localized pain with discrete tender areas rather than diffuse, widespread symptoms. 3, 2

Etiology

The development of MPS involves multiple contributing factors:

• Muscle overuse or sustained contraction from repetitive activities or prolonged static postures is the primary mechanical trigger. 1, 2
• Postural imbalances that create chronic muscle strain and asymmetric loading patterns. 1
• Acute trauma to muscles or fascia, including major injuries or minor dental procedures. 4
• Systemic conditions including bladder pain syndrome, endometriosis, and anxiety disorders are associated with increased MPS prevalence. 3
• Psychological and behavioral factors such as stress, poor coping strategies, and depression contribute to onset and chronicity. 1, 4

Pathophysiology

The exact mechanisms remain under investigation, but current understanding includes:

• Sustained muscle contraction leads to localized ischemia and energy crisis within muscle fibers, creating metabolically active trigger points. 2, 5
• Alterations in fascia including changes in collagen fiber composition, fibroblast dysfunction, and modifications in the hyaluronan-rich extracellular matrix. 6
• Sensitization of nociceptors within taut muscle bands produces both local tenderness and referred pain patterns through central nervous system mechanisms. 1, 5
• Autonomic nervous system involvement contributes to motor and sensory symptoms beyond simple pain. 6

Clinical Presentation

Pain Characteristics

• Location and pattern: Regional pain with specific trigger points that produce reproducible referred pain patterns when palpated. 1, 2
• Quality: Described as deep, aching, or burning pain that may be constant or intermittent. 7
• Aggravating factors: Prolonged postures, repetitive movements, stress, cold weather, and physical activity worsen symptoms. 4
• Relieving factors: Rest, heat application, and gentle stretching may provide temporary relief. 4

Associated Features

• Muscle stiffness and restricted range of motion in affected areas. 1
• Autonomic symptoms including altered sensation, muscle weakness, and fatigue. 6
• Sleep disturbances due to pain interfering with rest. 4, 7
• Psychological impact including mood changes, concentration difficulties, and reduced quality of life. 4, 7
• Co-existing conditions: Headaches, migraines, temporomandibular disorders, and other chronic pain syndromes frequently coexist. 4, 3

Diagnostic Criteria

There are no universally accepted diagnostic criteria for MPS, making diagnosis primarily clinical based on history and physical examination findings. 2

Essential History Components

• Timing: Document onset, duration, and periodicity of pain episodes. 4
• Pain characteristics: Assess location, radiation patterns, quality, and severity using validated tools like the Brief Pain Inventory or McGill Pain Questionnaire. 7
• Functional impact: Evaluate effects on sleep, mood, concentration, fatigue, and quality of life. 4, 7
• Contributing factors: Identify bruxism, clenching habits, postural habits, occupational activities, and psychological stressors. 4, 7
• Comorbidities: Screen for other pain conditions, depression, anxiety, and systemic diseases. 4

Physical Examination Requirements

• Extraoral assessment: Visual inspection for asymmetry, swelling, or color changes; palpation of muscles of mastication, head and neck muscles for tenderness, trigger points, and hypertrophy. 4, 7
• Trigger point identification: Palpate suspected areas (trapezius, levator scapulae, rhomboids, subscapularis, masseter) to identify taut bands with at least one localized trigger point that reproduces the patient's pain. 8, 2
• Range of motion testing: Assess temporomandibular joint movement, including crepitus, clicking, or locking. 4
• Neurological examination: Evaluate cranial nerves to exclude neuropathic causes. 4

Differential Diagnosis Considerations

• Giant cell arteritis must be excluded in patients over 50 years presenting with facial or temporal pain. 4, 7
• Malignancy can present as progressive neuropathic pain and must be considered with red flag symptoms. 4
• Fibromyalgia presents with diffuse, widespread pain rather than localized trigger points. 2
• Neuropathic pain conditions including trigeminal neuralgia and post-traumatic neuropathy have distinct characteristics. 4

Rehabilitation Treatment

Manual physical therapy techniques targeting trigger points should be the initial treatment approach for MPS, as they provide the largest reduction in pain severity with minimal risk of harm. 4, 9, 7

First-Line Conservative Treatments (Initiate These First)

Manual Physical Therapy (Strongest Evidence)

• Manual trigger point therapy provides pain reduction approximating twice the minimally important difference compared to placebo. 4, 9
• Myofascial release techniques to address connective tissue restrictions and fascial dysfunction. 9, 7, 8
• Muscle contracture lengthening through specific manual techniques. 4, 9
• Therapist-assisted jaw mobilization for temporomandibular involvement. 4

Treatment protocol: 10 sessions of 60 minutes over 12 weeks demonstrated 59% of patients reporting moderate or marked improvement. 4

Supervised Exercise Programs

• Low-resistance exercise to improve joint stability by increasing muscle tone. 9
• Supervised jaw exercise and stretching (with or without manual trigger point therapy) provides important pain relief approximating 1.5 times the minimally important difference. 4
• Supervised postural exercise to address biomechanical contributors. 4, 9
• Avoid pelvic floor strengthening exercises (e.g., Kegel exercises) as they may worsen symptoms. 4

Patient Education and Self-Management

• Education on condition, prognosis, and self-care strategies is essential for all patients. 4, 9
• Home exercises and stretching programs as part of usual care. 4, 9
• Self-massage techniques for symptom management between therapy sessions. 4

Second-Line Pharmacological Options (After Conservative Measures)

Topical Treatments (Preferred for Safety)

• Lidocaine patches for localized pain relief. 9, 8
• Diclofenac patches as topical NSAID option. 9, 8
• Capsaicin cream may provide relief for some patients. 9

Oral Medications

• NSAIDs for symptomatic relief during acute exacerbations; document trial and response. 9, 8
• Tricyclic antidepressants may benefit patients with chronic symptoms. 9
• SNRIs (serotonin-norepinephrine reuptake inhibitors) as alternative to tricyclics. 9
• Anticonvulsants (gabapentin, pregabalin) for persistent pain with neuropathic features. 9
• Muscle relaxants for documented muscle spasm; trial before considering injections. 8

Important caveat: Evidence for NSAIDs, muscle relaxants, antidepressants, and gabapentin in MPS is insufficient or inconclusive. 1 Use these as adjuncts to physical therapy, not as monotherapy.

Third-Line Adjunctive Therapies

Cognitive-Behavioral Interventions

• Cognitive behavioral therapy (CBT) provides pain reduction approximating 1.5 times the minimally important difference. 4
• CBT augmented with relaxation therapy or biofeedback provides the largest pain reduction (approximately twice the minimally important difference). 4, 9
• Breathing exercises and relaxation techniques for stress management. 9

Physical Modalities

• Heat and cold packs for symptomatic relief. 9
• Transcutaneous electrical nerve stimulation (TENS) may reduce pain, though evidence is insufficient. 7, 1
• Ultrasound therapy shows some evidence of effectiveness compared to sham. 1
• Low-level laser therapy may be effective but requires further study. 1, 2
• Extracorporeal shockwave therapy has some supporting evidence. 1, 2

Alternative Approaches

• Acupuncture shows some evidence of effectiveness compared to placebo. 1
• Dry needling has some supporting evidence but remains controversial. 1
• Kinesiology taping has inconclusive evidence. 1

Fourth-Line Interventional Procedures (Only After 3+ Months Conservative Treatment Failure)

Trigger point injections should only be considered as part of multimodal treatment after conservative measures have failed, and patients must continue concurrent physical therapy. 8

Trigger Point Injections

• Local anesthetic injections have sufficient evidence for effectiveness. 1
• Limit to 4 sets of injections maximum to assess therapeutic response. 8
• Target documented trigger points in trapezius, masseter, levator scapulae, rhomboids, or subscapularis muscles. 8
• Continue physical therapy concurrently as injections alone are insufficient. 8

Important limitation: Botulinum toxin injections show insufficient evidence for MPS. 1

Nerve Blocks (Generally Not Recommended)

• Peripheral somatic nerve blocks should NOT be used for long-term treatment of chronic pain. 8
• Supraorbital, supratrochlear, and occipital nerve blocks have insufficient evidence for MPS-related pain. 8

Treatment Algorithm

Step 1 (Weeks 0-12): Initiate manual physical therapy (10 sessions over 12 weeks) + supervised exercise program + patient education. 4, 9

Step 2 (If inadequate response at 12 weeks): Add topical analgesics (lidocaine or diclofenac patches) + consider oral NSAIDs for exacerbations. 9, 8

Step 3 (If inadequate response at 6 months): Add CBT with relaxation therapy or biofeedback + consider tricyclic antidepressants or SNRIs. 4, 9

Step 4 (If inadequate response after 3+ months of comprehensive conservative treatment): Consider trigger point injections (maximum 4 sets) while continuing physical therapy. 8

Common Pitfalls and Caveats

• Avoid monotherapy approaches: MPS requires multimodal treatment combining physical therapy, exercise, and behavioral interventions. 8, 2
• Do not rely on injections alone: Trigger point injections without concurrent physical therapy are insufficient and violate evidence-based guidelines. 8
• Avoid premature procedural interventions: Conservative treatment must be attempted for at least 3 months before considering injections. 8
• Do not prescribe pelvic floor strengthening exercises: These may worsen symptoms in patients with pelvic floor involvement. 4
• Recognize chronicity risk: Early intervention is critical as MPS becomes increasingly refractory to treatment in the chronic stage. 2
• Screen for red flags: Always exclude giant cell arteritis (age >50), malignancy, and serious neurological conditions. 4, 7
• Address comorbidities: Depression, anxiety, and other chronic pain conditions must be managed concurrently for optimal outcomes. 4, 3
• Avoid overreliance on diagnostic testing: MPS is a clinical diagnosis; imaging is not routinely indicated unless red flags are present. 7

Cost and Access Considerations

Most effective treatments (manual physical therapy, supervised exercise, CBT) require clinician administration and patient participation, with costs potentially borne by patients depending on insurance coverage. 4 However, these conservative approaches have minimal risk of harm and provide the best evidence for meaningful pain reduction. 4, 9