Leg cramps, or charley horses, are a common problem that affect the feet, calves, and thigh muscles. They involve sudden, painful involuntary contractions of a leg muscle.
They often occur while a person is sleeping or resting. They can be gone in a few seconds, but the average duration is 9 minutes. They can leave tenderness in the muscle for up to 24 hours after.
In most cases the reason for leg cramps is never found, and they are considered harmless. Sometimes, however, they may be linked to an underlying disorder, such as diabetes or peripheral artery disease.
Fast facts on leg cramps
Here are some key points about leg cramps. More detail is in the main article.
Leg cramps most commonly affect the calf muscle.
They typically only last a few minutes, but the pain can last for 24 hours.
They are more common in older age and during pregnancy.
Most often, leg cramps are no cause for concern and have no medical significance.
Risk factors may include dehydration, some medications, flat feet, and alcohol abuse.
Cramps are generally not a sign of an underlying condition.
In most cases, there is no underlying cause and the reason why cramps happen is unclear.
They are thought to be caused by muscle fatigue and nerve dysfunction, but exactly how they happen is unclear.
It has been suggested that the way we sleep, with the foot stretched out and the calf muscles shortened, may trigger night cramps. Another theory is that cramps are more likely nowadays, as people no longer squat, a position that stretches the calf muscles.
Exercise is one factor. Stressing or using a muscle for a long time may trigger a leg cramp during or after the exertion. Cramps often affect athletes, especially at the start of a season, if the body is out of condition. Nerve damage may play a role.
Dehydration is thought to play a role. Athletes who exercise strenuously in hot weather often experience cramps. However, there is a lack of evidence to confirm this, and the theory has been disputed. Athletes who play in cool climates also get cramps, after all.
Sometimes the leg cramps are caused by an underlying condition, situation or activity.
Other conditions that may cause cramps are:
gastric bypass surgery
hypothyroidism, or an underactive thyroid
chronic kidney failure
type 2 diabetes
sarcoidosis, a disease in which small growths or lumps produce inflammation or swelling of the tissues in any part of the body
vascular disease and venous insufficiency
motor neuron problems
oral birth control
peripheral artery disease (PAD)
pregnancy, especially in the later stages
use of some medications, including intravenous iron sucrose, conjugated estrogens, naproxen, raloxifene, and teriparatide
Cramps have been linked to electrolysis imbalances, but reseach has not supported these theories.
Older people are more likely to experience leg cramps. Muscle loss starts from the mid-40s and increases if the person is not active. This increases the risk of cramps.
Between 50 and 60 percent of adults and 7 percent of children are believed to experience cramps, and the likelihood increases with age.
They are more common during pregnancy.