Not Medical Advice: Nighttime leg cramps are usually sudden spasms, or tightening, of muscles in the calf. The muscle cramps can sometimes happen in the thigh or the foot. They often occur just as you are falling asleep or waking up.
A muscle cramp, also known as charley horse, is a strong, painful contraction or tightening of a muscle that comes on suddenly and lasts from a few seconds to several minutes.
The cause of muscle cramps isn't always known. It may be brought on by many conditions or activities, including:
Exercising, injury, or overuse of muscles.
Pregnancy. Cramps may occur because of decreased amounts of minerals, such as calcium and magnesium, especially in the later months of pregnancy.
Exposure to cold temperatures, especially to cold water.
Other medical conditions, such as blood flow problems (peripheral arterial disease), kidney disease, thyroid disease, and multiple sclerosis.
Standing on a hard surface for a long time, sitting for a long time, or putting your legs in awkward positions while you sleep.
Not having enough potassium, calcium, and other minerals in your blood.
Being dehydrated, which means that your body has lost too much fluid.
Taking certain medicines, such as antipsychotics, birth control pills, diuretics, statins, and steroids.
You can learn more about muscle cramps at WebMD.
When muscle cramps strike, there are ways you can do to ease the pain and get moving again. Try these tips for relief shared by Mayo Clinic.