How can I differentiate between nocturnal leg cramps and other causes of leg pain in my patients?

Differentiating nocturnal leg cramps from other causes of leg pain involves careful clinical assessment of the characteristics and context of the pain.

• Typical features of nocturnal leg cramps: sudden, painful, involuntary contractions of the calf or foot muscles occurring at night, often waking the patient from sleep. The cramps usually last a few minutes and resolve spontaneously or with stretching and massage of the affected muscle.

• Idiopathic nature: In many cases, nocturnal leg cramps are idiopathic, with no underlying serious cause, and are common from age 18 onwards.

• Absence of systemic or neurological signs: Unlike other causes of leg pain, nocturnal leg cramps do not typically present with altered consciousness, anuria, fever, or neurological deficits. Presence of such signs may indicate systemic disorders or neurological disease requiring further investigation or referral.

• Duration and frequency: Nocturnal cramps are usually brief and episodic, whereas other causes of leg pain (e.g., peripheral vascular disease, neuropathy, musculoskeletal disorders) may cause persistent or activity-related pain.

• Response to stretching: Stretching and dorsiflexion of the ankle often relieve cramps, which is less typical for other causes of leg pain.

• Investigations: If the diagnosis is uncertain or if there are atypical features, consider investigations such as serum creatine kinase, electromyography, nerve conduction studies, or specialist referral to exclude muscle disease or lower motor neuron disease.

Summary: Nocturnal leg cramps are characterised by sudden, brief, painful muscle contractions at night, relieved by stretching, without systemic or neurological signs. Other causes of leg pain often have different patterns, associated symptoms, or signs that warrant further assessment or referral.

For more detailed guidance on assessment, management, and when to refer, see the CKS Leg cramps topic.