Four reasons your legs cramp at night

Nocturnal leg cramps are involuntary, often painful contractions of the calf or foot muscles that occur at rest, usually at night. They typically last seconds to a few minutes and leave the muscle tender afterwards.

Most are benign. The pattern matters more than the single episode — and in most cases the cause traces back to how the muscle was loaded, positioned or supplied during the day.

The four common causes

1. Prolonged or awkward sittingSitting for hours with the knees bent and feet unsupported keeps the calf shortened. A muscle held short all day is more likely to cramp when it finally relaxes.
2. A sedentary lifestyleMuscles that are rarely loaded lose conditioning and tolerance. Deconditioned calves fatigue and cramp more readily than trained ones.
3. Pregnancy or altered nerve activityCramping is common in later pregnancy, driven by circulatory and mineral changes. Nerve irritation from the lower back can also present as calf cramping.
4. Knee hyperextension and sleeping positionSleeping with the knees locked straight and toes pointed puts the calf in its shortest position, which is where cramps most often start.

What usually helps

• Stretch your calves and hamstrings before bed, holding 30 seconds each
• Keep the duvet loose so your feet are not forced into a pointed position
• Break up long periods of sitting — stand and move every 45 minutes
• Build gradual calf strength: heel raises, progressed slowly
• Stay adequately hydrated across the day, not just in the evening

When to have it checked

• Cramps that occur most nights and disturb sleep persistently
• Cramping with numbness, tingling or weakness in the leg
• Calf pain with swelling, warmth or redness — this needs same-day medical review
• Cramps that started after a new medication