A nighttime leg cramp, commonly called a "charley horse," is a painful contraction of muscles in the leg that happens suddenly and involuntarily. According to Mayo Clinic.com, no cause is known for most leg cramps, and they are usually harmless. The risk of nighttime leg cramps increases with age and during pregnancy. In rare cases, they can be associated with a serious condition such as diabetes or peripheral vascular disease. Consult a physician to determine the cause.
Diseases
Some diseases are known to cause nighttime, or nocturnal, leg cramps. Conditions that potentially reduce circulation, such as diabetes and peripheral artery disease, or PAD, can result in leg cramps. New York University's Langone Medical Center lists Parkinson's disease, a thyroid imbalance or other hormonal disorder, and low blood sugar, or hypoglycemia as other diseases that can cause leg cramps. ALS, or Lou Gehrig's disease, spinal nerve irritation or compression, called radiculopathy, stenosis, or a narrowing of the spinal canal, chronic infections, liver disease can cause leg cramps to develop.
Medications
Some medications can cause nocturnal leg cramps. NYU explains that statins, or medications that lower cholesterol, blood pressure medications, morphine and lithium potentially cause cramps. Diuretics, also called water pills, some asthma medicines such as terbutaline and salbutamol and nifedipine, a blood pressure medicine, can contribute to nighttime leg cramping, according to a 2005 article in "British Journal of General Practice" by Richard J Coppin, B Med Sci, DRCOG, et al.
Electrolyte Imbalances
Electrolye imbalances, or disturbances in the chemistry of the body, can cause abnormal muscle cramping, explains the American Academy of Orthopedic Surgeons, or AAOS. Normal balance of sodium, potassium, magnesium, calcium and other minerals are affected by sweating from exercise in hot weather, dehydration, diuretics and kidney failure or dialysis.
Other Possible Causes
Other possible causes of nighttime leg cramps include overexertion of muscles during exercise, standing on hard surfaces, prolonged sitting and certain leg positions maintained while sedentary. The AAOS notes that poor physical condition, inadequate stretching and muscle fatigue can cause cramps as well.
