The painful condition commonly called a charley horse is the result of a muscle spasm that uncontrollably forces a muscle into contraction without allowing it to relax, according to the University of Maryland Medical Center. One of the possible causes for the spasm could be an irritated nerve connected to the muscle. Exercising while dehydrated or a lack of minerals, such as potassium or calcium, are other possible causes.
A charley horse muscle spasm often involves a calf muscle and can occur while in bed. This type of a spasm can also appear in back muscles as a result of nerves irritated by a herniated disc. Muscle spasms in the neck area can be the result of stress and upper leg muscle spasms can be caused by jumping or running activities.
Massaging the affected muscle may bring relief from the pain and, if an activity was taking place, it should be stopped at the first onset of discomfort. In the case of severe or repeated occurrences, the sufferer should consult a health care provider. Physical therapy, or possibly surgery, may be required if there is an irritated nerve.
The term "charley horse" is colloquial to North America and the condition may also be described as a "muscle knot." Some colorful euphemistic terms can be found outside of the North American area for this type of a muscle spasm. The condition is known as a "corky" in Australia and in Scandinavia, it's called a "wooden leg," "thigh cookie" or "thigh hen." Depending on the region of Italy, the muscle spasm can be referred to as a "water buffalo," "old woman" or "donkey bite."