what causes cramp

About leg cramps

Leg cramps are a common and usually harmless condition where the muscles in your leg suddenly become tight and painful.

It usually occurs in the calf muscles, although it can affect any part of your leg, including your feet and thighs.

After the cramping has passed, you may have pain and tenderness in your leg for several hours.

Three out of four cases occur at night during sleep.

Read more about the symptoms of leg cramps.

What causes leg cramps?

Leg cramps can occur for no apparent reason, known as idiopathic leg cramps, or as a symptom or complication of a health condition, known as secondary leg cramps.

Causes of secondary leg cramps can include:

• pregnancy
• exercise 
• certain types of medication, such as statins (medicines that help lower cholesterol levels)
• liver disease

During a cramp, your muscles suddenly contract (shorten), causing pain in your leg. This is known as a spasm, and you cannot control the affected muscle.

The cramp can last from a few seconds to 10 minutes. When the spasm passes, you will be able to control the affected muscle again.

Read more about the causes of leg cramps.

When to see your GP

Speak to your GP if your leg cramps are affecting your quality of life; for example, if you have frequent leg cramps or they are interfering with your sleep.

Your GP will ask about your symptoms and examine your legs and feet. They may also ask if you have other symptoms, such as numbness or swelling, which may be a sign that you have secondary leg cramps caused by an underlying condition.

In this case, you may need further tests, such as blood tests and urine tests, to rule out other conditions.

Treating leg cramps

Most cases of leg cramps can be relieved by exercising the affected muscles. Exercising your legs during the day will often help reduce how often you get cramping episodes.

• Stretches

To stretch your calf muscles, stand with the front half of your feet on a step, with your heels hanging off the edge. Slowly lower your heels so that they are below the level of the step. Hold for a few seconds before lifting your heels back up to the starting position. Repeat a number of times.

Medication is usually only needed in the most persistent cases where cramping does not respond to exercise.

If you have secondary leg cramps, treating the underlying cause may help relieve your symptoms.

Leg cramps that occur during pregnancy should pass after the baby is born.

Treating cramps that occur as a result of serious liver disease can be more difficult. Your treatment plan may include using medications such as muscle relaxants.

Read more about treating leg cramps

• Preventing leg cramps

If you often get leg cramps, regularly stretching the muscles in your lower legs may help prevent the cramps or reduce their frequency.

You might find it useful to stretch your calves before you go to bed each night (see stretching advice above or try this post-exercise calf stretch).

The following night-time advice may also help:

• If you lie on your back, make sure that your toes point upwards – placing a pillow on its side at the end of your bed, with the soles of your feet propped up against it may help keep your feet in the right position. 
• If you lie on your front, hang your feet over the end of the bed – this will keep your feet in a relaxed position and help stop the muscles in your calves from contracting and tensing.
• Keep your sheets and blankets loose.

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