GPAtlas🧭 When to suspect
A leg cramp is a sudden, involuntary, painful contraction of a muscle, most often the calf, but also the foot or thigh. Episodes typically last from seconds to ten minutes, leave the muscle visibly hard and tender, and may be followed by residual soreness for up to 24 hours. They are very common, occur predominantly at night or at rest, and rise sharply with age – more than a third of people over 60 are affected.
The two clinical tasks in primary care are to confirm that this is a true cramp (a palpable, painful contraction relieved by stretching – not the urge-to-move of restless legs syndrome, the exertional pain of claudication, or a neuropathic dysaesthesia), and then to separate idiopathic (primary) cramps – benign and the large majority – from secondary cramps driven by a drug or an underlying condition. A focused search for a secondary cause, and exclusion of dangerous mimics such as deep vein thrombosis (DVT), peripheral arterial disease (PAD) and cellulitis, does most of the diagnostic work.
| Common drug causes | Common medical (secondary) causes |
|---|---|
|
• Diuretics (loop and thiazide) – via electrolyte and fluid loss • Statins – more often myalgia than true cramp • Beta-agonists (e.g. salbutamol) • Nifedipine and other calcium-channel blockers • Raloxifene and nicotinic acid |
• Pregnancy – around a third in the third trimester • Peripheral arterial disease and chronic venous disease • Chronic kidney disease / haemodialysis (cramps in ~50% with uraemia) and liver cirrhosis • Hypothyroidism (cramps in 20–50%) and diabetic peripheral neuropathy • Electrolyte disturbance (low sodium, calcium, magnesium or potassium); dehydration or salt depletion after heavy or hot-weather exertion • Motor neurone disease (MND) and other neuromuscular disorders |
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🧠 Clinical pearl The commonest misdiagnosis is restless legs syndrome mislabelled as cramp – and it leads to inappropriate quinine. Restless legs is an urge to move with an unpleasant crawling sensation that is worse at rest and relieved by movement, with no painful contraction. A true cramp is the opposite: a visible, palpable, painful spasm relieved by stretching the muscle. |
Source: NICE
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