Muscle cramps

What are muscle cramps?¹

Muscle cramps are very common and 'cramp' is usually taken to mean 'a spasmodic, painful, involuntary contraction of skeletal muscle'. Cramps usually last for a few seconds (but may last up to several minutes) and cease spontaneously, although pain and tenderness may persist for several hours afterwards.

The lower limbs are almost invariably involved. Most leg cramps occur when at rest during the night, but some people experience daytime cramps, especially if there is an underlying cause.

There are many causes. Cramps can be grouped according to their underlying aetiology:

• Paraphysiological cramps

• Symptomatic cramps

• Idiopathic cramps

When patients complain of cramps it is important to clarify exactly what they mean, as the term is frequently used to describe any muscular 'tightness'.

Muscle cramp epidemiology

Groups at increased risk of muscle cramps:

• Up to 60% of adults report that they have had nocturnal leg cramps.²

• The problem is often distressing, impacting on sleep, and has an adverse effect on quality of life.

• Pregnant women - up to 30% of women can be affected by leg cramps during pregnancy.³

• Muscle cramps are common in children, especially at night.

• Those with metabolic disorders; for example, 50% of patients with uraemia and 20-50% of those with hypothyroidism complain of muscle cramps.¹

• Athletes and individuals working under hot conditions - eg, firemen.

History

Find out what the patient means by cramps:

• Where do they occur?

• When do they occur?

• How often do they occur?

• How long do they last?

• Is there any other relevant medical history such as thyroid disease or cardiovascular disease?

• Are drugs taken? For example, diuretics, salbutamol, nifedipine.

• What is their alcohol consumption?

• Do they undertake any sporting activities?

Most often, cramps involve the calf or thigh muscles and small muscles of the foot. Of these, the most commonly affected is the calf and it tends to be unilateral.

Examination

• During an attack the affected muscle or group is hard and tender.

• Between attacks examination is unlikely to be rewarding.

• The muscle may be tender for up to 24 hours after the previous attack.

• In the elderly or where peripheral arterial disease is suspected, check for peripheral pulses and capillary refill.

• Look for signs of neurological disease - eg, muscle wasting and fasciculations, altered reflexes, sensory or power loss.

Paraphysiological cramps

• Paraphysiological cramps occur in healthy people in response to a physiological stimulus. They are very common and may occur during sport or in unaccustomed exercise. They are especially likely to occur during endurance sports.

• They are also very common in pregnancy.

• They may occur as a result of a sustained posture over a prolonged period of time.

Symptomatic cramps

Cramps may also occur in association with metabolic disturbance, including:

• Hyponatraemia

• Hypokalaemia and hyperkalaemia

• Hypocalcaemia

• Hypomagnesaemia

• Hypoglycaemia

One or more of these may be the underlying aetiology in many of the causes listed below. Blood tests measure the extracellular environment but do not reflect the intracellular fluid which is probably more important.

• Peripheral arterial disease.

• Acute or chronic diarrhoea.

• Excessive heat and sweating causing sodium depletion.

• Hypothyroidism (associated with weakness, enlarged muscles and painful muscle spasms).

• Hyperthyroidism (associated with myopathy).

• Lead poisoning.

• Sarcoidosis.

• Hyperparathyroidism (hypercalcaemia).

• Heavy alcohol ingestion and cirrhosis.

• Hyperventilation-induced respiratory alkalosis.

• Haemodialysis.

• Parenteral nutrition.

• Lower motor neurone disorders including amyotrophic lateral sclerosis, polyneuropathies, recovered poliomyelitis, peripheral nerve injury and nerve root compression.

Idiopathic cramps¹

This is a diagnosis of exclusion but represents the majority of those experiencing the condition. Familial forms exist which appear to have an autosomal dominant mode of transmission.⁴ This group also contains conditions such as idiopathic nocturnal cramps and fasciculation-cramp syndrome.

Differential diagnosis¹

Includes:

• Restless legs (Ekbom's syndrome).

• Peripheral arterial disease: intermittent claudication and ischaemic rest pain.

• Muscle injury or strain.

• Hypnagogic muscle jerking (when falling asleep).

• Sciatica: lumbar nerve root entrapment.

• Ruptured Baker's cyst.

• Deep vein thrombosis or thrombophlebitis.

• Peripheral neuropathy.

• Occupational cramps - eg, writer's cramp or musician's cramp (focal dystonias, usually affecting the upper limb).

• Causes of generalised muscle pain - eg, polymyositis, toxoplasmosis, alcohol-related myopathy, Guillain-Barré syndrome, polymyalgia rheumatica, Parkinsonism, fibromyalgia.

Investigations

Usually no investigation is indicated. They may be performed if an underlying cause is suspected. Initial investigations may include:

• U&Es

• LFTs

• TFTs

• Serum calcium or magnesium

• Creatine kinase

• Lead levels

Any further investigations will depend on any suspected underlying cause and will usually be performed in secondary care.

Muscle cramp treatment and management

Limited evidence supports treating nocturnal leg cramps with exercise and stretching, or with medications such as magnesium, calcium-channel blockers, vitamin B or vitamin C. Quinine is no longer recommended to treat leg cramps.²

General

• In most cases the aetiology is benign and the patient needs to be reassured of this whilst steps are taken to help alleviate the problem. Exclude known causes of muscle cramps without excessive and unnecessary investigation.

• Management depends upon the cause of the problem. Review drugs. Address any correctable problems - eg, use of diuretics and electrolyte imbalance.

• The severity of symptoms and their impact on sleep, mood and quality of life will determine whether treatment is required.

• The evidence base for management of this common but usually benign condition is not strong.

Non-drug

A Cochrane review found that a combination of daily calf and hamstring stretching for six weeks may reduce the severity of night-time lower limb muscle cramps in people aged 55 years and older, but the effect on cramp frequency is uncertain. The review otherwise found only limited evidence for the use of non-drug therapies for the treatment of lower-limb muscle cramps.⁵

Advise:

• Passive stretching and massage of the affected muscle. This will help ease the pain of an acute attack - eg, for calf cramping, straighten the leg with dorsiflexion of the ankle or heel walk until the acute pain resolves.

• Regular stretching of the calf muscles throughout the day. This may help to prevent acute attacks. Some people recommend stretching three times daily whilst others advocate stretching before going to bed.

• Using a pillow to raise the feet through the night or raising the foot of the bed. This may help to prevent attacks in some people.

Diagram of a Stretching Exercise

Whilst stretching exercises are unlikely to do harm, evidence for their efficacy is contradictory. In sport, stretching is widely advocated as likely to reduce injury and cramp but the quality of evidence tends to be poor, with failure to distinguish benefit from that due to improvement in physical fitness from training.⁶ Avoiding over-training and risky conditions (eg, hot and humid environmental conditions) can be useful in preventing cramps.⁷

The value of massage, over and above psychological benefit, is also questioned.⁸

Drugs¹

• Quinine sulfate has been the most frequently used drug in the UK for the treatment of leg cramps in non-pregnant individuals who have not responded to conservative measures.

• A Cochrane review found that there was moderate evidence that quinine significantly reduces cramp frequency, intensity and cramp days in dosages between 200 mg and 500 mg/day. There was moderate evidence that with use up to 60 days, the incidence of serious adverse events was not significantly greater than for placebo in the identified trials.⁹

• However quinine is generally not recommended for treating idiopathic leg cramps due to the poor benefit-to-risk ratio. A trial of quinine may be considered if:

  • Treatable causes of cramp have been excluded. Leg cramps are very painful and frequent.

  • Cramps affect the person's quality of life (particularly sleep disturbance).

  • Self-care measures, such as stretching exercises, are ineffective.

• Quinine has been associated with dose-dependent QT-interval-prolonging effects, and should be used with caution in patients with risk factors for QT prolongation (see the article on Torsades de Pointes for further information on risk factors for prolonged QT interval), or in those with atrioventricular block.¹⁰

• If quinine treatment is thought to be appropriate:

  • Prescribe 200-300 mg (at bedtime) for four weeks.

  • Ask the person to monitor any benefit using a sleep and cramp diary.If no benefit is seen after four weeks, stop treatment.

  • If beneficial, continue for three months, then aim to stop treatment to reassess ongoing need.

  • If further treatment is required, review every three months and continue to consider stopping treatment to assess ongoing need.

  • Advise not to exceed the recommended dose as serious adverse effects may occur. If signs of thrombocytopenia occur during treatment (eg unexplained petechiae, bruising or bleeding), advise seeking urgent medical advice.

• Quinine can frequently be stopped without a recurrence of troublesome symptoms.¹¹

• Avoid quinine in pregnancy and concentrate on non-drug measures where possible. The evidence is unclear as to whether any intervention provides effective treatment for leg cramps in pregnancy.¹² There is no evidence that magnesium supplementation is effective prophylaxis for older adults experiencing skeletal muscle cramps.¹³