Why do leg cramps happen at night? An orthopaedic doctor explains

From nerve misfiring to sleeping position, night-time leg cramps have many triggers. A doctor explains what causes them and when they need medical attention

Have you ever experienced a sudden, painful leg cramp, the sharp tightening in the calf that wakes you up in the middle of the night? You stretch, rub, mutter, wait for it to pass, and probably blame low water intake for it.

 

While dehydration or low minerals are often blamed, according to Dr Tarun Suri, Professor & Head of Orthopaedics & Ortho Spine Surgery, Amrita Hospital, Faridabad, the real reasons are more complex and have much to do with how nerves and muscles behave during sleep.

What is happening inside your body during a night-time leg cramp?

According to Dr Suri, the strongest explanation for night cramps lies in over-excited motor nerves, particularly at the level of the spinal cord. Under normal circumstances, your spinal cord sends both “go” and “stop” signals to muscles. During sleep and rest, the inhibitory or braking signals become quieter. Because of this, the motor neurons begin firing repeatedly, which causes the muscle to contract.

 

 

“At night, muscle tone drops, sensory input decreases, and your limbs often remain in shortened positions for hours. With less feedback from the body’s internal sensors, the nervous system’s ability to regulate itself weakens. The muscle locks into a painful, sustained contraction,” he explains.

Is dehydration really to blame for night cramps?

Dehydration has become the default explanation for cramps and is also usually wrong.

 

Most people who experience night-time leg cramps are not clinically dehydrated. Drinking more water may help some, but it rarely solves the problem completely.

 

Dr Suri says dehydration matters mainly when it disrupts fluid and electrolyte balance, such as in people taking diuretics, those with kidney disease, or during prolonged illness. In otherwise healthy individuals, dehydration is often not the main cause.

 

He further highlights that even magnesium, potassium and other electrolytes, while important, are often over-blamed.

Do circulation problems or long sitting hours play a role?

While they can play a role, they are rarely the primary cause, says Dr Suri.

 

He explains, “Poor venous return or chronic venous insufficiency may lead to muscle hypoxia and metabolite build-up, making nerves more irritable at night. Peripheral artery disease is more strongly linked to pain during walking, but in advanced cases, cramps at rest or at night can occur.”

 

Long hours of sitting shorten calf muscles and reduce neuromuscular adaptability. When those shortened muscles are suddenly stretched during sleep, cramps can be triggered. 

Can your sleeping position or bedding trigger leg cramps?

“Yes,” says Dr Suri.

 

During sleep, many people point their toes downward, a position known as plantar flexion, which shortens the calf muscles. This places muscle spindles in a position that makes reflex contraction more likely.

 

Tight bed sheets or mattresses that keep the foot in this shortened position can also act as triggers, especially if you are already prone to cramps.

Why do night cramps become more common with age?

According to Dr Suri, ageing alters the neuromuscular system. There is a gradual loss of inhibitory spinal neurons, making motor nerves easier to excite. Muscles become less elastic. Motor units remodel, with fewer and larger units firing together. All of this lowers the threshold for involuntary contraction.

Can medicines cause night-time leg cramps?

Dr Suri says certain medicines can contribute to night-time leg cramps. Several commonly used drugs that can increase cramp risk include:

• Diuretics, which can alter fluid and electrolyte balance
• Statins, which may affect muscle membranes or mitochondrial function
• Beta-agonists, which increase nervous system excitability
• Some calcium channel blockers, which alter ion handling in muscle cells

However, if cramps are persistent or severe during the course of treatment, a medication review is essential, Dr Suri stresses. 

When should night cramps raise red flags?

Occasional cramps are common, but if there is a pattern or if the cramps are worsening, medical evaluation is necessary. Consider underlying conditions if cramps occur alongside:

• Sensory changes or autonomic symptoms (diabetes)
• Fatigue and fluid imbalance (kidney disease)
• Stiffness, weight gain and cold intolerance (hypothyroidism)
• Asymmetry, gait changes or altered reflexes (neuropathy or spinal issues)

How can you ease a leg cramp when it strikes?

According to Dr Suri, to ease a cramp immediately, gently straighten the leg and pull the toes towards the shin to stretch the calf, then massage the muscle until it relaxes. Standing up and placing weight on the cramped leg, followed by gentle stretching, can also help stop the cramp.

 

Dr Suri says understanding why leg cramps occur at night helps take the fear and confusion out of a painful experience. Knowing the triggers allows people to focus on practical steps rather than quick fixes that may not work.

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