Low Back Cramps and Spasms

What a back spasm feels like

A lower back spasm can feel like a tight knot, a cramp, a grabbing or "electric" jolt, or the whole lower back locking up. You may be stuck bent forward or leaning to one side. Moving, coughing or getting out of a chair can trigger another wave. Between spasms there is often a dull ache and stiffness. The muscles may feel hard and tender to the touch.

Common causes of low back cramps

Muscle strain and overuse

The most common cause. Lifting something heavy or awkwardly, twisting, a sudden movement, unaccustomed exercise or gardening can overstretch the back muscles. The muscle tightens to protect itself. See muscle strain.

Protective spasm around a disc or joint

When a disc, facet joint or ligament in the spine is irritated, nearby muscles clamp down to splint it. This is why spasm often accompanies a herniated disc or acute low back pain. Pain or tingling spreading down the leg points to nerve involvement, such as sciatica.

Posture and inactivity

Long periods of sitting, driving or standing in one position tire the back muscles. Weak core and gluteal muscles make spasms more likely.

Dehydration and electrolyte imbalance

Heavy sweating, not drinking enough, diuretics, and low potassium, magnesium or calcium can make muscles more prone to cramping.

Menstrual cramps

Period pain often spreads to the lower back as a cramping ache, starting just before or with the period and lasting 1 to 3 days. See dysmenorrhea.

Pregnancy

Hormonal loosening of ligaments, weight gain and posture changes cause back pain and muscle spasms, especially in later pregnancy.

Less common causes

• Kidney stones: waves of severe pain in the side and back, spreading to the groin, with nausea and sometimes blood in the urine. Pain does not change with position.
• Kidney infection: back or side pain with fever and urinary symptoms.
• Ankylosing spondylitis: chronic inflammatory back pain and stiffness in younger adults.
• Spinal stenosis: cramping in the back and legs on walking, eased by sitting or bending forward, in older adults.
• Medicine side effects: statins and some diuretics can cause muscle cramps.
• Serious causes: spinal infection, fracture, tumor and cauda equina syndrome are rare but important.

Muscle spasm vs other back pain

How to relieve a lower back spasm

Right now

1. Find a comfortable position: lie on your back with your knees bent over pillows, or on your side with a pillow between your knees.
2. Apply heat: a heat pack or warm shower for 15 to 20 minutes relaxes the muscle. Ice can help in the first day if there is a strain.
3. Breathe slowly and deeply to help the muscle let go.
4. Take an OTC pain reliever: NSAIDs such as ibuprofen or naproxen work better than acetaminophen for back pain. Follow the label dose. Avoid NSAIDs if you have stomach ulcers, kidney disease, heart failure or take blood thinners.
5. Move gently as soon as you can: short walks every hour or two.

Over the next days

• Stay active. Bed rest slows recovery. Return to normal activity gradually.
• Gentle stretches: knee-to-chest, pelvic tilts, and cat-cow, within comfort.
• Hydrate and eat potassium- and magnesium-rich foods if you have been sweating heavily.
• Massage or a physical therapist can help release tight muscles.
• Prescription muscle relaxants are sometimes used for a few days for severe spasm. They cause drowsiness and are not for long-term use.

Preventing back spasms

• Strengthen your core and gluteal muscles: bridges, planks and bird-dogs.
• Lift with your legs, keep loads close to your body, and avoid twisting while lifting.
• Take breaks from sitting every 30 to 60 minutes.
• Warm up before exercise and build intensity gradually.
• Keep a healthy weight and stay active.

Diagnosis

Most back spasms do not need tests. A clinician asks how it started and screens for red flags: leg weakness, numbness, bladder or bowel changes, fever, weight loss, cancer history, injury and age. They examine your back, leg strength, reflexes and sensation. X-rays, MRI or blood tests are only needed when red flags are present or symptoms persist beyond 4 to 6 weeks.

Frequently asked questions

What causes lower back spasms?

Most are caused by straining the back muscles through lifting, twisting, overuse or prolonged sitting. Muscles also spasm to protect an irritated disc or joint. Dehydration, electrolyte imbalances, period cramps and pregnancy are other common causes. Rarely, spasms signal kidney stones or a spinal problem.

How long do lower back spasms last?

An acute back spasm usually eases within a few days, and most episodes of acute low back pain improve substantially within 2 to 6 weeks. Staying active speeds recovery. Spasms that keep returning or last longer than a month should be assessed.

What is the fastest way to relieve a back spasm?

Get into a position that eases the pain, apply heat, take an NSAID such as ibuprofen if it is safe for you, breathe slowly, and start gentle movement as soon as possible. Short, frequent walks help more than lying in bed.

What does an electric spasm in the lower back mean?

A sudden electric jolt may be a muscle spasm, but electric or shooting pain spreading into the buttock or leg suggests an irritated nerve root, as in sciatica from a herniated disc. If it comes with leg numbness, weakness or bladder changes, seek medical care promptly.

Should I use heat or ice for a back spasm?

Heat usually helps a muscle spasm more, by relaxing the muscle and easing pain. Ice can reduce pain in the first 24 to 48 hours after a strain. Use either for 15 to 20 minutes at a time with a cloth between it and your skin.