Myalgia and Myositis

Muscle Pain, Muscle Ache, Muscle Inflammation

What is Myalgia and myositis?

Myalgia means muscle pain or aching. Myositis means muscle inflammation. Since these terms refer to a symptom (pain) and a body response (inflammation) and are associated with a wide variety of disorders, a specific diagnosis is required.

Myalgia and myositis may occur either together or independently. Painful muscles are not always inflamed. Likewise, muscle inflammation sometimes causes weakness instead of pain. Causes of myalgia and/or myositis range from localized muscle injury to systemic disorders. Localized muscle injury includes overexertion (such as after unaccustomed exercise or following the intense contractions of a seizure), trauma to the muscle by over stretching or overloading (strains and sprains), and direct injury to the muscle (bruises, cuts, or crushing injuries).

Systemic disorders that may cause myalgia and/or myositis include viruses (influenza, Epstein-Barr, herpes simplex, poliomyelitis), bacterial infections (strep throat, Lyme disease, tetanus), fungi (histoplasmosis), and parasites (malaria, toxoplasmosis, trichinosis). Myalgia and/or myositis can also be caused by immunizations (vaccination against a variety of diseases), medications (anticonvulsants, antibiotics, anticancer agents, cholesterol-lowering agents, diuretics), substance abuse (alcohol, amphetamines, cocaine, narcotics), and poisons (strychnine, snake, insect or spider bites). Deficiencies in vitamin C and B-complex, as well as mineral and electrolyte deficiencies (calcium, magnesium, phosphorus, potassium, sodium), can cause muscle myalgias.

Myalgia can also be the result of certain endocrine and metabolic disorders such as hypothyroidism, hyperthyroidism, Addison's disease, hypoparathyroidism, diabetes mellitus, and diabetic neuropathy. Connective tissue diseases (also called collagen vascular diseases) are a group of inflammatory disorders whose symptoms may include myalgia and myositis such as rheumatoid arthritis, systemic lupus erythematosus, polymyositis, dermatomyositis, and polymyalgia. In central nervous system disorders, myalgia may be related to spasticity (multiple sclerosis, amyotrophic lateral sclerosis, spinal cord injuries) or rigidity (Parkinson's disease). Other conditions in which myalgia and/or myositis may be present include sarcoidosis (a systemic disease of unknown cause), compartment syndrome (where pressure from swelling within a closed tissue space compromises circulation and nerve function), several inherited metabolic disorders, eosinophilia-myalgia syndrome, and psychogenic myalgia (muscle pain with no apparent physical basis).

How is it diagnosed?

Myalgia and myositis are symptoms, not a diagnosis. Therefore, it is the underlying cause or condition that must be identified.

History: A description of the symptoms should include location, severity, and quality (dull, aching, cramping, stiffness, weakness). Individuals may report a precipitating event such as trauma, insect bite, drug ingestion, or recent immunization. Other symptoms may include fever, chills or sweats, weight loss, joint pain or stiffness, neurological symptoms (numbness, tremor, visual disturbances, ringing in the ears), depression, sleep disturbances, fatigue, rash, or respiratory, cardiac, or gastrointestinal symptoms. The history should include information regarding the onset (sudden or gradual) and type (constant or intermittent) of symptoms.

Physical exam: The gait, posture, and coordination is observed for any abnormal movements. Muscles are inspected for any evidence of wasting (atrophy), enlargement (hypertrophy) or permanent shortening (contracture). Muscle tone (natural tension) and strength are assessed through range-of-motion and resistance exercises. Examination by touching (palpation) may reveal tenderness or abnormal muscle tension (spasm). Joint disease is ruled out by examining joints for swelling, redness, accumulations of fluid (effusion), localized tenderness, increased temperature, and joint mobility.

Tests: Blood tests are used to detect inflammation and to rule out underlying conditions. These may include a complete blood count (CBC), ESR (erythrocyte sedimentation rate), electrolytes, hormone levels, various chemistries (calcium, phosphate, serum enzymes), and serological tests. An elevated ESR indicates an inflammation or infection, or an underlying malignancy. A serum enzyme (creatine kinase) is elevated when there is muscle injury or breakdown of muscle tissue (rhabdomyolysis). Serological tests detect antibodies in the blood and are used to diagnose infections, parasitic infestations, or connective tissue disease. A urine test is also helpful in the diagnosis of muscle disorders. Myoglobinuria (the presence of a muscle protein in the urine) is indicative of muscle tissue breakdown. Cultures of body fluids or tissues can identify bacterial infections, fungi, and viruses.

Electromyography (EMG) measures the electrical activity of muscle. Although an abnormal EMG can be due to either a muscle or a nerve disorder, the type of abnormality revealed can differentiate between the two. X-ray, CT, and bone scan can diagnose bone and joint disorders, differentiating them from muscle disorders. Muscle biopsy may be indicated in the diagnosis of inherited metabolic disorders, connective tissue disease, eosinophilia-myalgia, sarcoidosis, and trichinosis.

How is it treated?

Treatment depends on the specific diagnosis. Nonspecific myalgias (due to overexertion, systemic viral infection, or immunization) can usually be relieved by over-the-counter analgesics.


Motrin (Ibuprofen), Ultram (Tramadol), Aleve (Naproxen)

What might complicate it?

Complications are determined by specific diagnosis.

Predicted outcome

Since myalgia and myositis are symptoms of an underlying condition, prognosis depends on the specific diagnosis. Nonspecific myalgia due to overexertion or immunization is usually mild and self-limited. Myalgia accompanying systemic infection resolves with the underlying infection.


Joint disease will have similar symptoms.


Physical therapy, three times a week, for a period of four to six weeks.

Appropriate specialists

Orthopedist, physiatrist, and internist.

Learn more about

  • Pain Management
  • Pain Basics
  • Fibromyalgia

Last updated 12 July 2015


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