Muscle cramps are mostly benign and self-limited, but may also be indicative of a wide variety of potentially serious systemic disorders.
Idiopathic (ordinary) muscle cramps are common, short-lived, and usually involve the calf muscle and/or foot.
The diagnostic approach for idiopathic muscle cramps is one of exclusion. Cramps due to known pathologies can be ruled out reasonably quickly and easily by medical history and targeted physical exam.
Nonpharmacologic therapy forms the cornerstone of management of muscle cramps in the acute phase. Passive and/or active stretching of the affected muscle(s) is by far the most effective and safest therapy for most acute idiopathic muscle cramps.
Data are extremely sparse regarding ongoing prevention of muscle cramps. With the exception of drug therapies targeted at underlying/precipitating conditions, there are no proven, specific, effective, and safe drug therapies for muscle cramps. Quinine is used in some countries for the prevention of idiopathic cramps, but is associated with serious side effects (e.g., cardiac arrhythmias, thrombocytopenia, hepatotoxicity, blindness). Therapeutic trialing of various medications used for symptomatic benefit is a reasonable approach.
A muscle cramp is a sudden, involuntary, painful muscle contraction or spasm, associated with an increase in frequency of motor action potentials. Idiopathic (ordinary) muscle cramps are common.
About 80% of episodes involve the gastrocnemius, with a mean duration per episode of 8 to 9 minutes in adults and 2 minutes in children.
The focus of this topic is true cramps (motor unit hyperactivity). These are most commonly idiopathic cramps, but can be associated with other conditions.
History and exam
Key diagnostic factors
- concurrent hemodialysis (organic cause)
- cirrhosis (organic cause)
- pregnancy (idiopathic cramp)
- strenuous exercise (idiopathic cramp)
- medication use (idiopathic cramp)
- nocturnal onset (idiopathic cramp)
- gastrocnemius muscle involvement, with or without foot involvement (idiopathic cramp)
- duration <10 minutes (idiopathic cramp)
- unilateral (idiopathic cramp)
- precipitation by both trivial movements and forceful contractions (idiopathic cramp)
- visible or palpable muscular knotting
- good response to passive/active stretching (idiopathic cramp)
- normal neurologic exam (idiopathic cramp)
- normal general physical exam (idiopathic cramp)
- other local muscle involvement (neuromuscular disease cramp)
- widespread muscle cramps (lower motor neuron disease)
- duration >10 minutes (organic cause)
- abnormal neurologic exam (organic cause)
- abnormal musculoskeletal exam (organic cause)
Other diagnostic factors
- signs of a chronic medical condition (organic cause)
- strenuous exercise
- beta-blockers with intrinsic sympathomimetic activity
- age >60 years
- female sex
- family history of cramp
- other agents
- hypoglycemia in patients with diabetes mellitus
- chronic diseases
- home parenteral nutrition
1st investigations to order
- clinical diagnosis
Investigations to consider
- serum or urine hCG
- fasting serum metabolic panel
- thyroid-stimulating hormone (TSH)
- serum liver function tests
- prothrombin time (PT) and INR
- serum myoglobin and urinalysis
- serum creatine kinase (CK)-MM
- serum alpha-tocopherol (vitamin E)
- serum zinc
- nerve conduction studies
- serum aldolase
- muscle biopsy
- genetic studies
hypoglycemia-associated in diabetes mellitus
multiple sclerosis- or lower motor neuron disease-associated
- Occupational cramps
- Assessment: symptomatic treatment for muscle cramps (an evidence-based review)
- Practice parameter update: the care of the patient with amyotrophic lateral sclerosis: multidisciplinary care, symptom management, and cognitive/behavioral impairment (an evidence-based review)
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