Leg cramps: causes and when they are a warning sign

At night the calf suddenly tightens into a hard knot, the foot twists, and for a few seconds you can neither stand up nor breathe. Then it lets go — leaving a sore muscle and the question of what that was. Most often it is an ordinary cramp, but sometimes a disease is hiding behind it.

What a leg cramp is

A cramp is a sudden involuntary painful contraction of a muscle or part of it, in which a hardening can be seen or felt. It lasts from a few seconds to 10 minutes, after which the muscle may remain sore for up to 24 hours.

Most often the calves are affected — the muscle at the back below the knee; less often the muscles of the feet and thighs. Cramps differ from spasm (any involuntary contraction, not necessarily painful), contracture (a painful contraction without electrical activity of the muscle), and dystonia. The unpleasant sensations of restless legs syndrome are also not considered a cramp.

What causes leg cramps: main causes

The cause of some cramps remains unknown: such cases are linked to exertion, pregnancy, and age and are called idiopathic, because no pathology is visible behind them.

• age — night cramps are more common in older people;
• muscle overexertion during exertion, especially in heat and high humidity;
• dehydration, when the body lacks fluid;
• certain medications, for example cholesterol-lowering drugs and diuretics;
• pregnancy, usually in the later stages.

Liver disease due to alcohol abuse is also named separately. Another layer of causes is the level of electrolytes and minerals: potassium, calcium, magnesium; vitamin D deficiency; thyroid disorders; chronic kidney disease and dialysis. Why a cramp occurs the way it does is not fully understood: some studies indicate that the nerve activity in it originates in the spinal cord.

Night cramps and cramps during pregnancy

Cramps occur at any time of day, but most people notice them at night or at rest; night leg cramps are a common complaint in older people.

During pregnancy they usually appear in the later stages, more often in the third trimester. This is a typical situation when no cause is found and they are called idiopathic cramps.

Diseases in which the legs cramp

Cramps and spasms can be a symptom of a number of diseases: neurological — Parkinson's disease, multiple sclerosis, dystonia, Huntington's disease; damage to the nerves that connect them to the muscles (mononeuropathy and polyneuropathy).

Other causes include chronic kidney disease and dialysis, thyroid disease, vitamin D deficiency, hyperventilation — rapid or deep breathing during anxiety and a panic attack. Symptoms depend on the cause: muscle tightening, fatigue, weakness, numbness, tingling, twitching, involuntary rapid movements.

How a doctor determines the cause

The doctor examines and asks questions: when the cramps occur, how long they last, what preceded them, what medications the person takes. Blood and urine tests are ordered: potassium, calcium, and magnesium, hormones, kidney function markers, vitamin D level (25-OH vitamin D).

If a nerve or muscle disease is suspected, electroneuromyography is performed — a test of nerve conduction and electrical activity of muscles.

When cramps require seeing a doctor

A cramp by itself is most often harmless and resolves on its own. A reason to see a doctor is if cramps disrupt sleep, if numbness or swelling of the legs appears along with them, or if an episode lasts longer than 10 minutes.

If spasms recur, the cause is investigated separately — and the decision on examination is made by the doctor.

A leg cramp by itself is not a reason to call an ambulance: it usually passes within a few seconds or minutes. 103 or 112 are needed if signs of a stroke or heart attack appear at the same time — conditions in which help is required immediately.

This text is for reference: it does not replace a doctor's consultation but explains what to talk about at an appointment.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer