Myalgia (Muscle Pain) — Complete Clinical Guide
Full clinical coverage: differential diagnosis, detailed investigations, medicine dosing (adult & pediatric), rehabilitation, nutrition, prevention, and linked resources for deeper reading.
Contents — Jump to
- Definition & classification
- Epidemiology & clinical significance
- Causes (detailed)
- Pathogenesis & pathology
- Clinical features & red flags
- Differential diagnosis & important mimics
- Investigations — bedside, lab, imaging, special tests
- Management — algorithmic & medicines with dosing
- Inflammatory myopathies & immunosuppressive therapy
- Rehabilitation & physiotherapy
- Nutrition & supplements
- Complications, prognosis & follow-up
- When to refer / red flags
- Internal links — related posts
- References & disclaimer
Definition & classification
Myalgia = subjective muscle pain. It is a symptom, not a diagnosis. It can be classified by duration (acute < 2–4 weeks; subacute 4–12 weeks; chronic >12 weeks), distribution (localized vs generalized), and mechanism (inflammatory, metabolic, infectious, drug-induced, traumatic).
Note: Myalgia may coexist with true muscle weakness — always document whether weakness (objective) is present, because that differentiates neuropathic/neuromuscular pathology from simple muscle pain.
Epidemiology & clinical importance
Myalgia is extremely common: seen in viral illnesses (influenza, COVID-19), statin therapy adverse effects, electrolyte disturbances, and systemic inflammatory disorders. While most cases are benign and self-limiting, some indicate serious disease (rhabdomyolysis, polymyositis, dermatomyositis, electrolyte emergencies) and require urgent work-up.
Causes — comprehensive list with examples
1. Infectious
- Viral: Influenza, COVID-19, Dengue, Enteroviruses, HIV seroconversion.
- Bacterial: Sepsis-related myalgias, pyomyositis (Staph aureus), Lyme disease.
- Parasitic: Trichinosis, malaria (with myositis).
2. Inflammatory / autoimmune
- Polymyositis, Dermatomyositis, Inclusion body myositis, SLE-associated myositis.
3. Drug & toxin induced
- Statins (myopathy/rhabdomyolysis), fibrates (esp. with statin combo), colchicine, antimalarials (chloroquine), certain antipsychotics, alcohol, illicit drugs.
4. Metabolic / endocrine
- Hypothyroidism (myalgic pain, cramps), hypocalcemia (tetany, cramp), hypokalemia (weakness/cramps), vitamin D deficiency.
5. Traumatic / Overuse
- Delayed onset muscle soreness (DOMS), traumatic tears, compartment syndrome.
6. Neuromuscular junction & neuropathic causes
- Myasthenia gravis (fatigue > pain), peripheral neuropathies can present with aching pain.
7. Functional / central sensitization
- Fibromyalgia (widespread myalgia with tender points), chronic fatigue syndrome.
Medication-induced myalgias are common — review drug list (statins, antivirals, immunomodulators). For statin-related muscle symptoms see baseline CK and consider switching agent or dose adjustment.
Pathogenesis & pathology
Pathways for pain generation:
- Peripheral nociception: muscle injury/inflammation → prostaglandins, bradykinin, cytokines activate nociceptors.
- Ischemic pain: intracompartmental pressure or vascular insufficiency.
- Metabolic derangements: electrolyte abnormalities disturb membrane potentials, causing cramps/pain.
- Immune-mediated: T-cell mediated muscle fiber injury (polymyositis) with MHC upregulation and complement activation (dermatomyositis).
Pathology findings (biopsy/histology)
- Polymyositis: endomysial lymphocytic infiltrate, fiber necrosis, MHC-I upregulation.
- Dermatomyositis: perivascular/perimysial inflammation, perifascicular atrophy, complement-mediated microangiopathy.
- Rhabdomyolysis: muscle fiber necrosis, myoglobin release — risk of acute tubular necrosis.
Clinical features — history & examination
History tips
- Onset: sudden vs gradual. Relation to exercise, trauma, new drug, infection.
- Distribution: proximal (shoulder/hip girdle → think inflammatory myopathy) vs distal vs focal (pyomyositis/tennis injury).
- Systemic symptoms: fever, rashes (heliotrope rash → dermatomyositis), weight loss.
- Medication history: statins, antivirals, antimalarials, fibrates, steroids.
Examination
- Inspection: swelling, erythema, rash (Gottron papules, heliotrope).
- Palpation: focal tenderness, warmth (infective), crepitus (trauma).
- Power testing: objective weakness (MRC grading) — differentiates myositis from simple myalgia.
- Neuro exam: reflexes, sensory signs to exclude neuropathy.
Red flags (seek urgent care)
- Severe muscle pain with dark urine (myoglobinuria) → rhabdomyolysis risk
- Acute compartment syndrome (severe pain out of proportion, tense swelling)
- Fever with focal muscle swelling/overlying erythema → pyomyositis/abscess
- Rapidly progressive weakness, respiratory muscle involvement
Differential diagnosis — brief
- Fibromyalgia (widespread pain, tender points, normal CK)
- Polymyalgia rheumatica (older adults: proximal stiffness, elevated ESR)
- Polymyositis / Dermatomyositis (objective weakness, high CK)
- Rhabdomyolysis (very high CK, myoglobinuria)
- Hypothyroid myopathy (TSH high, CK may be moderately elevated)
- Statin myopathy (temporal relation to statin)
Investigations — algorithm & interpretation
Start with baseline basic tests and escalate guided by red flags.
Immediate / bedside
- Vitals, pulse oximetry
- Urine dipstick for blood (if red → check myoglobin & send CK)
- Point-of-care glucose (hypoglycaemia can mimic weakness)
Laboratory panel
| Test | Why & Interpretation |
|---|---|
| CBC | Infection (leucocytosis), anemia contributing to fatigue |
| CK (Creatine Kinase) | Marker of muscle injury — markedly raised in rhabdomyolysis/myositis |
| CRP, ESR | Inflammation (elevated in inflammatory myopathies, infection) |
| Electrolytes (Na, K, Ca, Mg) | Electrolyte disturbances cause cramps/weakness (treat promptly) |
| LFT, RFT | Assess hepatic/renal function (important before medications & for rhabdomyolysis management) |
| Thyroid function tests (TSH, FT4) | Hypothyroidism causes myalgic symptoms |
| Autoimmune serology (ANA, myositis panel, Anti-Jo-1) | If suspicion of inflammatory myopathy |
| Urine myoglobin | Rhabdomyolysis indicator (may be negative early) |
| Viral serology (HIV, Hep B/C) | If clinical indication |
Imaging & speciality tests
- Chest X-ray/ultrasound if focal infection suspected
- MRI muscle — sensitive for myositis (muscle edema pattern)
- Electromyography (EMG) — distinguish neuropathic vs myopathic process
- Muscle biopsy — gold standard for inflammatory myopathies and certain metabolic myopathies
When to measure CK & how often?
In suspected myositis or rhabdomyolysis: baseline CK and repeat every 6–24 h depending on severity. CK >5–10×ULN suggests significant injury; CK >10,000 U/L raises strong concern for rhabdomyolysis and renal risk.
Management — algorithmic approach
Management depends on cause and severity. Below is a practical stepwise algorithm.
Step 1 — Immediate stabilization
- Airway/breathing/circulation if severe weakness/respiratory involvement
- Stop offending drug (e.g., statin) and potential interactants (fibrates, macrolides, azoles)
- Analgesia and symptomatic care (rest, heat/ice as appropriate)
Step 2 — Investigate & treat reversible causes
- Correct electrolytes (give calcium gluconate for symptomatic hypocalcemia — see Calcium Gluconate guide)
- Treat infection — targeted antibiotics for pyomyositis (IV flucloxacillin/cephalosporin) or antivirals for certain conditions if indicated
- Hydration & urine alkalinization in rhabdomyolysis to protect kidneys
Step 3 — Analgesics & anti-inflammatory therapy (common medicines & dosing)
Below are commonly used medicines with typical adult doses. Adjust for renal/hepatic impairment, age and local guidelines.
| Drug | Typical Adult Dose | Comments / Precautions |
|---|---|---|
| Paracetamol | 500–1000 mg PO q6–8h PRN (max 3–4 g/day) | Preferred first-line for mild-moderate pain; check liver function for chronic/high-dose use |
| Ibuprofen | 200–400 mg PO q6–8h (max 1200–2400 mg/day depending on guideline) | GI/renal caution; take with food |
| Diclofenac | 50 mg PO BD | GI/CV/renal risk — avoid long-term |
| Topical NSAIDs (diclofenac gel) | Apply as per product 3–4 times/day | Useful for localized pain with less systemic exposure |
| Muscle relaxant (e.g., cyclobenzaprine / tizanidine) | Cyclobenzaprine 5–10 mg at night; tizanidine 2–4 mg PRN | Sedation; avoid with other CNS depressants |
| Opioids (short-term severe pain) | Use as rescue: e.g., tramadol 50–100 mg PRN, or short course of weak opioid | Use minimal duration; monitor for dependence |
| Antihistamine (for allergy-associated symptoms) | Chlorpheniramine 4 mg PO q4–6h PRN | Sedating; caution driving |
If signs of severe inflammation (confirmed inflammatory myopathy) — systemic corticosteroids often indicated (see immuno section).
Step 4 — Specific therapy for important conditions
- Rhabdomyolysis: Aggressive IV fluids (isotonic saline), monitor urine output, serum CK, electrolytes; consider bicarbonate & mannitol in selected cases; urgent nephrology if rising creatinine or hyperkalemia. See emergency protocols.
- Pyomyositis/Abscess: IV antibiotics (cover Staph aureus; e.g., flucloxacillin/cefazolin) and surgical drainage if abscess.
- Polymyalgia rheumatica: low-dose oral corticosteroids (e.g., prednisolone 15–20 mg/day) with rheumatology follow-up.
- Inflammatory myositis: High-dose corticosteroids ± steroid-sparing agents (see below).
Inflammatory myopathies — diagnosis & immunosuppressive therapy
If inflammatory myopathy suspected (proximal weakness, high CK, MRI/EMG & biopsy supportive):
- Start high-dose corticosteroids: Prednisolone 0.5–1 mg/kg/day (typical adult 40–60 mg/day) — monitor response and taper gradually.
- If severe or steroid-refractory: add steroid-sparing agents — Methotrexate 15–25 mg weekly (with folic acid), Azathioprine 1–3 mg/kg/day, Mycophenolate mofetil 1–2 g/day.
- IVIG (2 g/kg divided over 2–5 days) for severe or refractory dermatomyositis or necrotizing autoimmune myopathy.
- Biologics (rituximab) occasionally used for refractory cases — specialist care.
Baseline TB/HBV/HCV screening prior to starting potent immunosuppression. Monitor CBC, LFTs, and for drug-specific adverse effects.
Rehabilitation & physiotherapy
Rehab is essential for recovery and prevention of chronicity.
- Acute phase: relative rest, pain control, avoid aggressive exercises during active inflammation.
- Recovery phase: graded active exercises, range-of-motion, strengthening (under physio guidance).
- Pain management techniques: heat, cold packs, TENS, stretching.
- Occupational therapy for ADL support in severe weakness.
Nutrition & supplements — supportive evidence-based guidance
Nutrition supports healing and reduces complications. Key points:
- Ensure adequate protein intake (1.0–1.5 g/kg/day) for muscle repair — dietary sources: dairy, eggs, fish, pulses. See detailed protein guide: Protein — role & sources.
- Correct vitamin D deficiency — test 25-OH D and supplement guided by level.
- Consider multivitamin support in malnutrition / chronic alcohol use — e.g., Alamin M Forte.
- Electrolyte repletion: potassium, magnesium and calcium if deficient; symptomatic hypocalcemia treat with IV Calcium Gluconate in emergent cases.
- Anti-inflammatory dietary components: omega-3 fatty acids (fatty fish, flaxseeds), antioxidants (fruits like guava, banana, anjeer), and phytochemicals (onion/allium benefits: Onion).
Avoid high alcohol intake and extreme fasting during recovery as they impair muscle repair and interact with drugs (eg. acetaminophen, statins).
Complications, prognosis & follow-up
Complications
- Rhabdomyolysis → Acute kidney injury
- Chronic disability & contractures (if severe prolonged myositis)
- Secondary infections (pyomyositis)
Prognosis
Depends on underlying cause: viral/DOMS → excellent recovery; inflammatory myopathies → variable (often chronic but treatable); rhabdomyolysis → recovery if renal complications prevented.
Follow-up schedule (practical)
- Acute benign myalgia: review in 1–2 weeks if unresolved
- Elevated CK / suspected myositis: follow CK every 1–2 weeks until trending down; rheumatology referral
- On immunosuppression: regular CBC, LFT, and specialist monitoring as per agent
When to refer — red flags for specialty care
- Rapidly progressive weakness / respiratory muscle involvement — refer to neurology/intensive care
- CK markedly elevated (>5000–10,000 U/L) or myoglobinuria — nephrology consult for rhabdomyolysis
- Suspected inflammatory myopathy — early rheumatology/neuromuscular referral
- Focal abscess / pyomyositis — surgical/orthopaedic referral
Internal links — further reading on this site
- Complete Medical Nutrition Guide — detailed nutrition & vitamins.
- Biotin deficiency — hair/skin/muscle relevance.
- Calcium Gluconate — hypocalcemia management.
- Naloxone dosing & device — for suspected opioid-related conditions.
- Chlorpheniramine (CPM) — allergy-related therapy.
- Alamin M Forte — multivitamin support.
- Fruit & functional food articles: Guava, Banana, Anjeer, Onion.
Tip: use these internal links to create focused landing pages for common drugs & nutrition topics linked in this guide.
References & disclaimer
- Clinical textbooks: Harrison’s Principles of Internal Medicine; Current Rheumatology and Neurology guidelines.
- Guidelines for rhabdomyolysis & inflammatory myopathies (ACR/EULAR guidance).
- Local formularies & product labels for dosing and contraindications.
Disclaimer: This page provides educational clinical information. Always individualize treatment and dosing based on patient weight, comorbidity, renal/hepatic function and local protocols. For prescription-level decisions consult specialist guidance.