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 older adults), 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, but cramping of other muscle groups is also possible.
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.
Cramping is more likely when people do things that they are not prepared for (eg, using muscles not commonly used to do a physical task, doing an exercise never done before).
Etiology of Muscle Cramps
The most common types of leg cramps are
Benign idiopathic leg cramps (leg cramps in the absence of a causative disorder, typically at night)
Exercise-associated muscle cramping (cramps during or immediately after exercise)
Although almost everyone has muscle cramps at some time, certain factors increase the risk and severity of cramps. They include the following:
Tight calf muscles (eg, due to lack of stretching, inactivity, or sometimes chronic lower leg edema)
Dehydration
Electrolyte abnormalities (eg, low body levels of potassium or magnesium)
Neurologic or metabolic disorders
Removal of a large volume of fluid during dialysis in patients with end-stage kidney disease
Some medications
Also, certain toxins can cause muscle cramps.
Evaluation of Muscle Cramps
Evaluation of muscle cramps focuses on recognition of what is treatable. In many cases, a disorder contributing to cramps has already been diagnosed or causes other symptoms that are more troublesome than cramps.
Cramps must be differentiated from claudication and dystonias; clinical evaluation is usually adequate.
History
History of present illness should elicit a description of cramps, including their duration, frequency, location, apparent triggers, and any associated symptoms. Symptoms that may be related to neurologic or muscle disorders can include muscle stiffness, weakness, pain, and loss of sensation. Factors that can contribute to dehydration or electrolyte or body fluid imbalances (eg, vomiting, diarrhea, excessive exercise and sweating, recent dialysis, diuretic use, pregnancy) are recorded.
Review of systems should seek symptoms of possible causes, including the following:
Amenorrhea or menstrual irregularity: Pregnancy-related leg cramps
Cold intolerance with weight gain and skin changes: Hypothyroidism
Weakness: Neurologic disorders
Pain or loss of sensation: Peripheral neuropathies or radiculopathies
Past medical history should include any disorders that can cause cramps. A complete history of medication and other substance use (eg, alcohol) is taken.
Physical examination
General examination should include the skin, looking for stigmata of alcohol use disorder, nonpitting edema or loss of eyebrow hair (suggesting hypothyroidism), and changes in skin moisture or turgor. A neurologic examination, including deep tendon reflexes, is done.
Pulses should be palpated, and blood pressure measured in all extremities. A weak pulse or low ankle:brachial blood pressure ratio in an affected limb may indicate ischemia.
Red flags
In patients with muscle cramps, the following findings are of particular concern:
Upper extremity or truncal involvement
Hyperreflexia or hyporeflexia
Muscle weakness
Fasciculations
Signs of alcohol use disorder
Hypovolemia
Pain or loss of sensation in a peripheral nerve, plexus, or root distribution
Interpretation of findings
Focal cramps suggest benign idiopathic leg cramps, exercise-associated muscle cramping, musculoskeletal abnormalities, peripheral nervous system causes, or an early degenerative disorder that can be asymmetric, such as a motor neuron disorder.
Focal hyporeflexia suggests a peripheral neuropathy, plexopathy, or radiculopathy.
In patients with diffuse cramps (particularly those who are tremulous), hyperreflexia suggests a systemic cause (eg, ionized hypocalcemia; sometimes alcohol use disorder, a motor neuron disorder, or a drug, although effects on deep tendon reflexes can vary by drug). Generalized hyporeflexia can suggest hypothyroidism and sometimes alcohol use disorder or be a normal finding, particularly in older patients.
A normal examination and compatible history suggests benign idiopathic leg cramps or exercise-associated muscle cramping.
Testing
Testing is done as indicated by abnormal clinical findings. No tests are routinely done.
Blood glucose, renal function tests, and electrolyte levels, including calcium and magnesium, should be measured if patients have diffuse cramps of unknown cause, particularly if hyperreflexia is present.
Ionized calcium and arterial blood gases (ABGs) to confirm respiratory alkalosis are measured if patients have tetany.
Electromyography is done if cramped muscles are weak.
MRI of the brain and often spinal cord is done if muscle weakness or neurologic signs indicate that the central nervous system is involved.
Treatment of Muscle Cramps
Stretching
Underlying conditions are treated when identified.
If a cramp occurs, stretching the affected muscles often relieves the cramp. For example, to relieve a calf cramp, patients can use their hand to pull the toes and foot upward (dorsiflexion).
Applying heat (eg, using a warm towel or heating pad, taking a warm bath or shower) or cold (eg, massaging the affected muscle with ice) may help ease pain.
Prevention of Muscle Cramps
Measures to prevent cramps include the following:
Gently stretching the muscles before exercising or going to bed
Drinking plenty of fluids (particularly beverages that contain potassium) after exercise
Not consuming stimulants (eg, caffeine, nicotine
Not smoking
Stretching the gastrocnemius muscles (runner’s stretch) is often useful. A person stands with one leg forward and bent at the knee and the other leg behind and the knee straight―a lunge position. The hands can be placed on the wall for balance. Both heels remain on the floor. The knee of the front leg is bent further until a stretch is felt along the back of the other leg. The greater the distance between the two feet and the more the front knee is bent, the greater the stretch. The stretch is held for 30 seconds and repeated 5 times. The set of stretches is repeated on the other side.
1]), but whether using it is worth the risk of adverse effects is unclear. These effects include nausea, vomiting, heartburn, dizziness, tremor, and possibly seizures.
Prevention references
1. El-Tawil S, Al Musa T, Haseeb Valli H, et alCochrane Database Syst Rev Apr 5 (4):CD005044, 2015. doi: 10.1002/14651858.CD005044.pub3
2. Kuwabara S, Misawa S, Tamura N, et alClin Neurophysiol 116 (2):284–289, 2015. doi: 10.1016/j.clinph.2004.08.014
Key Points
Leg cramps are common.
The most common causes are benign idiopathic leg cramps and exercise-associated muscle cramping.
Cramps must be differentiated from claudication and dystonias; clinical evaluation is usually adequate.
Stretching can help relieve and prevent cramps.
Medications are usually not recommended.
