Muscle cramps

[Lanell]

A muscle cramp (charley horse) is a sudden, brief, involuntary, painful contraction of a muscle or group of muscles. Cramps commonly occur in healthy people (usually middle-aged and elderly people), sometimes during rest, but particularly during or after exercise or at night (including during sleep). Leg cramps at night usually occur in the calf and cause plantar flexion of the foot and toes.
Other disorders can simulate cramps:

Dystonias can cause muscle spasm, but symptoms are usually more sustained and recurrent and involve muscles other than those affected by typical leg cramps (eg, neck, hand, face, muscles throughout the body).
Tetany can cause muscle spasm, but spasm is usually more sustained (often with repetitive brief muscle twitches); it is usually bilateral and diffuse, but isolated carpopedal spasm may occur.
Muscle ischemia during exertion in patients with peripheral arterial disease (claudication) may cause calf pain, but this pain is due to inadequate blood flow to muscles, and the muscles do not contract as with a cramp.
Illusory cramps are the sensation of cramps in the absence of muscle contraction or ischemia.