| ICD-10 | R25.2 |
|---|---|
| ICD-9 | 729.82 |
| DiseasesDB | 3151 |
| MedlinePlus | 003193 |
| MeSH | D009120 |
Cramps are unpleasant, often painful sensations caused by muscle contraction or over shortening. Common causes of skeletal muscle cramps include muscle fatigue, low sodium, and low potassium. Smooth muscle cramps may be due to menstruation or gastroenteritis.
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Causes of cramping include[1] hyperflexion, hypoxia, exposure to large changes in temperature, dehydration, or low blood salt. Muscle cramps may also be a symptom or complication of pregnancy, kidney disease, thyroid disease, hypokalemia, hypomagnesemia or hypocalcemia (as conditions), restless-leg syndrome, varicose veins,[2] and multiple sclerosis.[3]
Electrolyte disturbance may cause cramping and muscle tetany, particularly hypokalaemia and hypocalcaemia. This disturbance arises as the body loses large amounts of interstitial fluid through sweat. This interstitial fluid comprises mostly water and table salt (sodium chloride). The loss of osmotically active particles outside of muscle cells leads to a disturbance of the osmotic balance and therefore shrinking of muscle cells, as these contain more osmotically active particles. This causes the calcium pump between the muscle lumen and sarcoplasmic reticulum to short circuit; the calcium ions remain bound to the troponin, continuing muscle contraction.
As early as 1965, researchers observed that leg cramps and restless-leg syndrome result from excess insulin, sometimes called hyperinsulinemia.[4] Hypoglycemia and reactive hypoglycemia are associated with excess insulin (or insufficient glucagon), and avoidance of low blood glucose concentration may help to avoid cramps.
Smooth muscle contractions lie at treatment may be symptomatic of endometriosis or other health problems. Menstrual cramps may also occur before a female menstrual cycle.
Skeletal muscles can be voluntarily controlled. Skeletal muscles that cramp the most often are the calves, thighs, and arches of the foot. A so-called Charley horse, this kind of cramp is associated with strenuous activity and can be intensely painful—though skeletal cramps can occur while relaxing. Around 40% of people who experience skeletal cramps are likely to endure extreme muscle pain, and may be unable to use the affected limb. It may take up to seven days for the muscle to return to a pain-free state.
Nocturnal leg cramps are involuntary muscle contractions that occur in the calves, soles of the feet, or other muscles in the body during the night or (less commonly) while resting. The duration of nocturnal leg cramps is variable with cramps lasting anywhere from a few seconds to several minutes. Muscle soreness may remain after the cramp itself ends. These cramps are more common in older people.[5] They happen quite frequently in teenagers and in some people while exercising at night. The precise cause of these cramps is unclear. Potential contributing factors include dehydration, low levels of certain minerals (magnesium, potassium, calcium, and sodium), and reduced blood flow through muscles attendant in prolonged sitting or lying down. Nocturnal leg cramps (almost exclusively calf cramps) are considered 'normal' during the late stages of pregnancy. They can, however, vary in intensity from mild to extremely painful.
Various medications may cause nocturnal leg cramps:[6]
Besides being painful, a nocturnal leg cramp can cause much distress and anxiety.[7]
Usually, putting some pressure on the affected leg by walking some distance will end the cramp.[8]
Statins cause myalgia and cramps among other possible side effects, including substantially lowering blood glucose concentration.[9] Additional factors, which increase the probability for these side effects, are physical exercise, age, female gender, history of cramps, and hypothyroidism. Up to 80% of athletes using statins suffer significant adverse muscular effects, including cramps;[10] the rate appears to be approximately 10–25% in a typical statin-using population.[11][12] In some cases, adverse effects disappear after switching to a different statin; however, they should not be ignored if they persist, as they can, in rare cases, develop into more serious problems. Coenzyme Q10 supplementation can be helpful to avoid some statin-related adverse effects, but currently there is not enough evidence to prove the effectiveness in avoiding myopathy or myalgia.[13]
Skeletal muscles work as antagonistic pairs. Contracting one skeletal muscle requires the relaxation of the opposing muscle in the pair. Cramps can occur when muscles are unable to relax properly due to myosin fibers not fully detaching from actin filaments. In skeletal muscle, ATP must attach to the myosin heads for them to disassociate from the actin and allow relaxation — the absence of ATP in sufficient quantities means that the myosin heads remains attached to actin. An attempt to force a muscle cramped in this way to extend (by contracting the opposing muscle) can tear muscle tissue and worsen the pain. The muscle must be allowed to recover (resynthesize ATP), before the myosin fibres can detach and allow the muscle to relax.
Stretching may be helpful in treating simple muscle cramps [14]. With exertional heat cramps due to electrolyte abnormalities (primarily sodium loss and not calcium, magnesium, and potassium ) appropriate fluids and sufficient salt improves symptoms.[15]
Quinine is likely effective, however, due to side effects its use should only be considered if other treatments have failed and in light of these concerns.[16] Vitamin B complex, naftidrofuryl, lidocaine, and calcium channel blockers may be effective for muscle cramps.[16]
Adequate conditioning, stretching, mental preparation, and adequate fluid/electrolyte balance are likely helpful in preventing muscle cramps. [17].
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