What are the causes of muscle cramps?

Causes of Muscle Cramps

Primary Etiologic Categories

Muscle cramps arise from three main pathophysiologic mechanisms: electrolyte and metabolic disturbances, medication-induced effects, and neurologic hyperexcitability—with the specific cause determining the appropriate treatment approach. 1, 2

Electrolyte and Metabolic Causes

• Hypomagnesemia is a common reversible cause, particularly in patients with gastrointestinal losses, diuretic use, or alcohol use 1, 3
• Hypokalemia frequently causes cramps, especially in patients on diuretics or corticosteroids 3, 4
• Dehydration with sodium depletion triggers cramps through secondary hyperaldosteronism and worsened magnesium losses 3, 5
• Hypocalcemia and hypophosphatemia can contribute, though less commonly than magnesium and potassium abnormalities 6

Medication-Induced Cramps

• Diuretics (both loop diuretics and aldosterone antagonists) are among the most common medication causes, inducing cramps through volume depletion and electrolyte disturbances 5, 7
• Corticosteroids like prednisone cause cramps through potassium wasting and metabolic effects 4
• Statins and other lipid-lowering agents are well-documented causes 7
• Antihypertensives, beta-agonists, insulin, and oral contraceptives can all trigger cramping 7
• Alcohol acts as both a direct toxin and causes secondary electrolyte depletion 7

Disease-Specific Causes

• Liver cirrhosis with ascites causes cramps through diuretic therapy, hypoalbuminemia, and fluid/electrolyte shifts 5, 1
• Hemodialysis patients develop intradialytic cramps from rapid fluid shifts and electrolyte changes 1
• Hypothyroidism presents with muscle cramps as a cardinal symptom, along with fatigue and cold intolerance 5
• Diabetes mellitus causes cramps through neuropathy and metabolic disturbances 7

Neurologic Causes

• Radiculopathies compress nerve roots, leading to cramping in the affected distribution 7
• Peripheral nerve hyperexcitability syndromes cause spontaneous motor nerve firing 8, 2
• Amyotrophic lateral sclerosis and other motor neuron diseases produce severe, disabling cramps 8
• Parkinson's disease is associated with increased cramping frequency 7

Exercise-Associated Causes

• Muscle fatigue with shortened muscle contraction is the primary mechanism in exercise-associated cramps, occurring during or immediately after exertion 7, 9
• Heavy sodium losses in "salty sweaters" exercising in hot environments depletes critical electrolytes 3
• Inadequate training and premature fatigue predispose athletes to cramping 7
• The traditional "dehydration theory" has mixed evidence—some industrial and field studies support it, but laboratory models show dehydration doesn't consistently affect cramp threshold 9

Physiologic States

• Pregnancy is associated with increased cramping frequency, likely through electrolyte shifts and increased metabolic demands 8
• Normal aging increases cramp susceptibility, though the mechanism remains unclear 2

Metabolic Myopathies

• Glycogen storage diseases and mitochondrial disorders can present with exercise-induced cramping and contractures 7, 2
• Contractures (distinct from cramps) result from inability of muscle to relax normally and are generally myogenic rather than neurogenic 2

Critical Diagnostic Distinctions

The key clinical question is whether cramps are benign/idiopathic, exercise-induced, or symptomatic of underlying disease—this determines whether simple reassurance suffices or aggressive workup is needed. 2

• In cancer patients, cramps often represent unsuspected pathology from either the neoplastic process or treatment side effects, requiring thorough evaluation 6
• Vascular insufficiency can mimic cramping and must be excluded in appropriate clinical contexts 7
• Most athletes with exercise-associated cramps are healthy individuals without systemic illness, requiring only training and nutrition optimization 7