Charley horse

A charley horse is the common name for a muscle spasm, particularly in the leg. Muscle spasms can occur in any muscle in the body. When a muscle is in spasm, it contracts involuntarily and does not relax.

Causes, incidence, and risk factors 

Muscle spasms commonly occur when a muscle is over-used or injured. Working out when dehydrated or with low levels of potassium can also predispose a person to muscle spasms. Some spasms are caused when the nerve that connects to a muscle is irritated. The classic example of this would be a herniated disk irritating spinal nerves as they exit the back causing pain and spasm.

Spasms in the calf commonly occur while kicking during swimming and can also occur at night while in bed. Upper leg spasms are more common with running or jumping activities. Spasm in the cervical spine (neck) can be a sign of stress.

When a muscle goes into spasm it feels very tight and is sometimes described as a knot. Pain can be acute and debilitating depending on the severity and location of the spasm. Back spasms are notoriously painful but even leg cramps can sometimes reduce men to tears.

Signs and tests 
Muscle spasms are diagnosed by the presence of tight or hard muscles that are very tender to the touch. There are no imaging studies or blood tests that can diagnose this condition. If the spasm is caused by nerve irritation, such as in the back, an MRI may be helpful to determine the cause of the irritation.

At the first sign of a muscle spasm, stop your activity and try stretching and massaging the affected muscle. Heat will relax the muscle at first, although ice may be helpful after the initial spasm and pain has improved. If the muscle continues to be sore, non-steroidal anti-inflammatory medications may help with pain. In more severe cases, your health care provider may prescribe anti-spasm medications.

After initial treatment, the cause of the spasm should be determined to prevent it from recurring. If an irritated nerve is involved, physical therapy or even surgery may be necessary.

The most common cause of muscle cramps associated with sports activity is dehydration. Often, rehydration with water or sports drinks will resolve the cramping.

Expectations (prognosis) 
Muscle spasms will resolve with rest and time and the prognosis is excellent for the vast majority of people. Instituting proper training techniques should prevent spasms from becoming a chronic problem. If an irritated nerve caused the spasm, more extensive treatment may be required and results are more variable.

Calling your health care provider  
If you have a severe muscle spasm with uncontrollable pain, contact your health care provider for assistance. Even if your spasms are not severe, your health care provider can help you modify your exercise program to reduce the risk of spasms occurring in the future.


  • Stretch to improve flexibility.  
  • Modify your workouts to exercise within your capabilities.  
  • Drink plenty of fluids while exercising and increase your potassium intake (orange juice and bananas are great sources of potassium).


Johns Hopkins patient information

Last revised: December 8, 2012
by Brenda A. Kuper, M.D.

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