A muscle cramp is a strong, painful muscle contraction or tightening that comes on suddenly and lasts from a few seconds to several minutes. Soreness in the muscle may last for hours after the hard, tense cramp has stopped.
The cause of muscle cramps is not always known. Muscle cramps may be brought on by many conditions or activities, such as:
Exercising, injury, or overuse of muscles.
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.