Leg cramps: causes

, medical expert
Last reviewed: 05.09.2022

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Leg cramps occur when a skeletal muscle involuntarily contracts and exerts its maximum tension in the form of a sudden, often very painful, but short-lived spasm. Convulsive contractions most often occur in the calf muscles of the back of the leg, as well as the muscles of the foot, the hamstring muscle above the hamstring, or the quadriceps muscle in front of the thigh. [1]


As statistics show, almost six out of ten older adults often cramp their legs, primarily at night: three out of four cases occur during sleep.

At the same time, leg cramps in men occur almost three times less often than cramps in women.

By some estimates, peripheral arterial disease (vessels of the lower extremities) affects almost 10% of people over 55 years of age.

Febrile seizures affect about 2-5% of children under the age of five.

Causes of the leg cramps

According to medical experts, in many cases the causes of leg cramps are unknown, and such cramps are called idiopathic.

Among the identifiable causes, first of all, there is an excessive load on the muscles and an overstrain of the muscle fibers in the calf or in the back of the thigh (in the hamstring area) with the occurrence of leg cramps after training; develop severe cramps in the legs after running - intense painful contractions that usually occur with fatigue and / or overheating. Local cramps are observed when individual muscle groups are overstrained due to the performance of frequently repeated fast movements, which, in particular, explains leg cramps during orgasm during sex.

Muscle cramps in the lower extremities or  cramps , not associated with increased physical activity, can be due to many different reasons: night leg cramps occur due to uncomfortable body position, cooling or overheating in sleep, too soft or hard bed. At night, leg cramps are more common in people over 50 than in younger people, and more often in people who are overweight than those who are thin.

The main cause of leg cramps in the morning is considered to be a long awkward position of the legs during sleep, with squeezing of blood vessels.

Tonic cramps in the legs during the day occur when a person walks for a long time, stands on a hard surface for a long time, or is forced to sit for a long time. It often cramps the feet of those who suffer from flat feet or wear shoes that are too tight, and high heels only increase the risk of muscle cramps in the calves and feet.

Many have leg cramps in the water - the pool or natural reservoirs. What causes leg cramps when swimming? Experts associate them with the flexion of the sole of the foot during swimming - when all the muscles of the leg form a rigid line from the lower leg to the toes, which allows you to move in the water. But holding this position overstrains the muscles and can cause them to contract involuntarily - severe leg cramps. In addition, in cold water, due to the compression of blood vessels, the blood circulation speed decreases, and with insufficient oxygen supply to muscle tissues, neuromuscular conduction is disturbed.

These are the most common benign types of leg cramps.

Read also -  Why do my toes cramp

However, there are many conditions and pathologies in which cramps in the left, right legs or cramps in both legs are one of their symptoms. That is, they are considered secondary, and in such cases, the causes of leg cramps are associated with specific conditions or diseases.

Leg cramps after surgery are considered a side effect of pain medications for local anesthesia and general anesthesia.

Convulsions in a leg fracture occur when the bone has traumatic damage to the muscle fibers surrounding it and compression of the endings of the motor nerves.

As a result of the toxic effect of ethanol on the central nervous system with inhibition of nerve signals, a decrease in the level of electrolytes due to dehydration, as well as disturbances in regional blood circulation, leg cramps occur after alcohol intake (especially by chronic alcoholics). [2]

Muscle spasms in the form of convulsions can occur due to iatrogenic causes: with prolonged use of drugs such as selective beta-adrenergic agonists (bronchodilators), antidepressants of the SSRI group, barbiturates, lithium, statins, nicotinic acid, hormonal contraceptives, cytostatics (anticancer drugs). After prolonged use of diuretics, that is, after diuretics, leg cramps are associated with increased excretion of magnesium from the body and the development of  hypomagnesemia .

Pulling legs and leg cramps during pregnancy (especially in the later stages) - due to a decrease in the amount of magnesium and calcium in the blood - hypocalcemia. Foot cramps at night often occur in the third trimester of pregnancy due to the pressure of the uterus on the veins and the deterioration of the outflow of blood; this often causes cramps in the legs and groin. For more details, see -  Why does it bring legs together during pregnancy . And leg cramps after childbirth are the result of squeezing blood vessels and muscle tension in the pelvic region and thighs.

Leg cramps in a child can occur when the body is dehydrated (with vomiting and / or diarrhea); with vitamin deficiency; due to thyroid problems. In febrile conditions associated with infectious diseases, in children under five years of age, leg cramps and fever are combined. Such convulsions are called febrile.

Increased risk of leg cramps with parasites - parasitic invasions: ascariasis, trichinosis, echinococcosis.

Frequent leg cramps in the elderly may be due to natural shortening of the tendons (due to fluid loss) and a decrease in the elasticity of muscle fibers; also in old age, painful cramps in the calves (at rest) and anterior part of the tibialis muscle (after walking) can be noted, which are symptoms of idiopathic  neuropathy of the legs .

In addition to physical inactivity and age-related degenerative changes in the muscular nature, leg cramps in people over 50 occur due to  circulatory disorders in the legs . A common condition with poor blood circulation associated with atherosclerosis or venous insufficiency is leg cramps when walking with the appearance of pain and even temporary lameness. In the first case, poor blood circulation in the arteries of the legs in old age often correlates with problems of atherosclerotic changes in cerebral vessels, and experts consider sleep disturbances, persistent headaches, frequent dizziness and leg cramps to be the first signal of the risk of developing such a dangerous condition in the future as ischemic stroke.

People who complain of cramps and cold feet, as well as the fact that their legs hurt at rest, cramps in the evening, should be examined for  peripheral vascular disease of the legs  (which develops due to cholesterol deposits in the arteries of the lower extremities).

In the second case, these are leg cramps with varicose veins - varicose expansion of the superficial veins, which is accompanied by a deterioration in the outflow of venous blood from the legs and a violation of muscle trophism. These types of cramps usually affect the calf muscles and the quadriceps femoris, which are stretched through two joints, that is, leg cramps are noted above the knee, thigh.

Complaints of cramps and cold feet are associated with endocrinological problems: the presence of diabetes or hypothyroidism.

If there are symptoms such as convulsions and  numbness of the legs  (paresthesia), then there is a suspicion that this is the result of compression of the nerve endings, and osteochondrosis in the lumbar region with the development of radiculopathy may be the culprit.

Most often, such leg cramps are observed in diabetes due to neurological disorders -  diabetic neuropathy . Another causal risk factor for seizures in diabetics is  limb angiopathy , which develops as a result of a decrease in the intensity of capillary and arterial blood flow in the legs.

If the patient complains of cramps and burning in the legs, then this may indicate peripheral neuropathy - a violation of the transmission of nerve impulses, noted in diabetes, cancer, malnutrition, infectious inflammation, chemotherapy of malignant tumors. In healthy people, burning in the legs after cramps is associated with lactic acidosis, that is, the accumulation in the blood of lactic acid, a by-product of the breakdown of glucose, the breakdown of which (for energy) occurs during intense training.

Cramps of the legs and back, accompanied by numbness and tingling in the leg, can give an intervertebral or intervertebral hernia (as a result of dystrophic changes in the muscles and disorders of their innervation). And leg cramps with herniated discs are associated with pinched nerves or stenosis of the lumbar spine; nerve root compression is considered by neurologists as one of the predisposing factors for nocturnal leg cramps. [3]

If, in addition to the occurrence of convulsions, the legs fail, the patient does not exclude such pathologies as multiple sclerosis (an autoimmune disease of the nervous system, in which the nerve processes lose their myelin sheath and muscle functions are impaired with the development of spasticity) or  motor neuron disease .

Accompanied by involuntary contractions of muscle fibers - fasciculations - peripheral flaccid paresis, that is, a decrease in muscle tone in one or both legs, may indicate neurological problems such as amyotrophic lateral sclerosis or damage to the motor neurons of the spinal cord (motor neuropathy).

A list of the most likely causes of leg and arm cramps includes:

  • insufficiency of the parathyroid glands - hypoparathyroidism, due to which the level of calcium in the blood decreases;
  • chronic form of renal failure, leading to an increase in the content of phosphates in the blood;
  • lack of potassium;
  • dehydration or lack of fluid;
  • epilepsy (with tonic-clonic seizures);
  • alcoholic delirium;
  • anemia (iron deficiency or hemolytic);
  • multiple sclerosis;
  • hypoglycemia;
  • infections, primary tumors or brain aneurysm;
  • side effects of drugs.

Risk factors

Summarizing the etiology of leg cramps, doctors call the following risk factors for their occurrence:

  • overstrain of the muscles of the lower extremities;
  • sedentary lifestyle and obesity;
  • musculoskeletal injuries;
  • age-related degenerative changes in muscle tissues and tendons;
  • dehydration (dehydration) associated with both insufficient fluid intake and excessive sweating;
  • alcoholism;
  • flat feet, wearing unsuitable shoes;
  • low levels of electrolytes (magnesium, calcium, or potassium) in the blood;
  • vitamin deficiency (B6, D, E);
  • pregnancy;
  • high blood cholesterol;
  • the presence of neurological or metabolic disorders;
  • endocrine diseases (diabetes mellitus, hypothyroidism, hypoparathyroidism);
  • neuromuscular disorders, in particular neuropathy, myopathy, motor neuron disease;
  • compression of the spinal nerves;
  • cirrhosis of the liver;
  • chronic kidney failure and the effects of kidney dialysis (during which too much fluid is removed from the body, which upsets the balance of electrolytes);
  • Parkinson's disease, Huntington's disease;
  • the use of certain drugs.

Older people have a higher risk of leg cramps: closer to 50 years, muscle mass loss begins, and - if a person leads a sedentary lifestyle - this process progresses.


The biochemistry of muscle contraction is very complex, and how disturbances in the transmission of nerve impulses occur is not yet entirely clear. The mechanism of development of cramps of the lower extremities at night, that is, their pathogenesis, is explained by the fact that cramps occur when the gastrocnemius muscle - with the legs in a dream with half-bent knees and feet pointing down - is in a shortened position and can be spasmodic with any attempt to change position.

In addition, prolonged periods in the same position during sleep are accompanied by a slowdown in blood circulation and a decrease in oxygen levels in muscle tissues, which leads to cramps.

There are several versions of the pathogenesis of seizures during physical overexertion. Traditionally, these spasms are thought to result from dehydration, electrolyte imbalances (including magnesium, potassium, and calcium), buildup of lactic acid, or low levels of cellular energy (in the form of ATP). For example, if the body lacks magnesium, the contact of afferent and efferent neurons in neuromuscular cholinergic synapses is disrupted: the channels of presynaptic membranes cease to open, and this leads to an increase in the level of free acetylcholine, a mediator of nerve impulses in muscles, in the synaptic cleft.

It is assumed that the mechanism of seizures is associated with increased activity of the neuromuscular reflex arc of the CNS, due, on the one hand, to the inhibitory effect of the Golgi tendon organs, and, on the other hand, to hyperactivation of muscle spindles. [4]

Symptoms of the leg cramps

Leg cramps occur suddenly, but some patients claim that they can feel the first signs of crampy development in the form of fasciculations - twitching of muscle fibers.

The main symptoms of a cramp are a sharp tension, that is, a muscle contraction that causes pain. At the same time, the cramped muscle becomes hard (rigid), and it is impossible to relax it by an effort of will.

Does not release leg cramp for 20-30 seconds or several minutes; the cramp of the quadriceps femoris muscle lasts the longest.

After the cramp passes, aching pain in the muscle may be felt for some time.

Cramps in diabetes capture the muscles of the legs and feet and are accompanied by paresthesia (or hyperesthesia), and quite pronounced pain in the leg after a cramp with the inability to move normally can be observed for several hours. [5]

Complications and consequences

In cases of leg cramps after exercise, there are no negative health or medical consequences.

Leg cramps at night can worsen the quality of life by disturbing sleep.

It is not difficult to guess how dangerous leg cramps are, which can catch a person driving a car or swimming in a river...

The involuntary muscle contractions themselves have nothing to do with the consequences of diseases, one of the symptoms of which are cramps of the lower extremities. Although many of these conditions, such as peripheral vascular disease of the legs, are

Potentially disabling.

Diagnostics of the leg cramps

From a medical point of view, primary benign seizures are rarely a cause for concern, and diagnosis is required if non-exercise-related involuntary muscle contractions occur consistently.

Necessary tests for leg cramps: general and biochemical blood tests; on the level of sugar, creatine kinase, lactate dehydrogenase, electrolytes, parathyroid hormone, specific antibodies to helminths.

Instrumental diagnostics is also carried out:

  • muscle examination  (electromyography, ultrasound);
  • dopplerography and ultrasound of the vessels of the legs,  angiography .
  • MRI of the spinal cord is done if there is focal muscle weakness or neurological signs.

Differential diagnosis

Differential diagnosis is very important, since some disorders cause symptoms that resemble seizures: dystonia, spasticity (including myotonia), fasciculations, essential tremor, myokymia, tetany. As well as focal (focal) or partial convulsions in the legs, and clonic convulsions, characteristic of epilepsy and hyperkinesis, determined in epilepsy.

Leg cramps are different from a condition called restless leg syndrome.

Oftentimes, the exact cause of leg cramps is difficult to determine and may be due to a combination of various factors.

For example, the low-carb Kremlin diet, which, like the Atkins diet, is a keto diet, removes fluid from the body. As a result, those who adhere to such a diet for weight loss (consuming a lot of proteins and fats) develop not only constipation, but also leg cramps - as absorption of magnesium in the intestines is reduced.

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