Low Back Cramps or Spasms

What a back spasm feels like

A lower back spasm typically feels like a sudden grab or seizing of the muscles on one or both sides of the spine. You may:

• be unable to stand up straight, leaning to one side
• feel a hard, tender knot in the muscle
• have sharp pain with small movements, coughing or sneezing
• find it hard to get out of bed or a chair
• have waves of cramping that come and go

The pain is felt in the back, sometimes spreading into the buttocks. Pain shooting down the leg below the knee suggests a nerve is involved (sciatica).

Why lower back muscles spasm

A spasm is the muscle's protective reflex. When a structure in the back is strained or irritated, nearby muscles contract to splint it and limit movement. The spasm itself then becomes painful.

Common causes

• Muscle strain or ligament sprain: from lifting heavy objects, lifting while twisting, a sudden movement, or unaccustomed activity such as gardening, moving house or sport.
• Disc irritation: a bulging or herniated disc can trigger strong protective spasms, sometimes with leg pain.
• Facet joint irritation: the small joints at the back of the spine can lock or become inflamed.
• Poor posture and prolonged sitting: muscles fatigue and tighten.
• Weak core muscles and deconditioning.
• Dehydration, heavy sweating and low electrolytes can make cramps more likely.
• Stress, which increases muscle tension.

Less common but important causes

How to relieve a lower back spasm

First 48 hours

• Keep moving gently. Short walks every hour are better than bed rest. Bed rest for more than a day or two slows recovery.
• Find a comfortable position: lying on your back with knees bent over pillows, or on your side with a pillow between your knees.
• Heat: a heating pad or warm bath for 15 to 20 minutes eases muscle spasm. Some people prefer ice in the first day; use what helps.
• Pain relief: an NSAID such as ibuprofen or naproxen can reduce pain and allow movement; follow the label dose and avoid them if you have kidney disease, stomach ulcers, are pregnant or take blood thinners. Acetaminophen (paracetamol) alone is less effective for back pain but may be used.
• Gentle stretches once the worst spasm settles: knee-to-chest, pelvic tilts and gentle cat-cow movements, within comfort.

Over the next 2 weeks

• Gradually return to normal activities, including work.
• Avoid heavy lifting and twisting until the pain eases.
• Use good lifting technique: bend at the knees and hips, keep the load close, avoid twisting.
• Take regular breaks from sitting.

Medical treatments

• Muscle relaxants may be prescribed for a short course for severe acute spasms. They cause drowsiness and are not for long-term use.
• Physical therapy: exercises, manual therapy and education, especially if pain persists beyond a few weeks.
• Massage, spinal manipulation and acupuncture have modest evidence for some people.
• Opioids are generally avoided for acute low back pain.

How doctors assess back spasms

The doctor will ask how the pain started, where it spreads, and about leg symptoms, bladder and bowel function, fever, weight loss and cancer history. They will examine your spine, check leg strength, reflexes and sensation, and perform a straight leg raise test.

Most people with back spasms do not need imaging. X-rays and MRI scans are reserved for red flags or for persistent nerve symptoms when surgery or injections are being considered, because scans often show age-related changes that are not causing the pain.

Preventing future spasms

• regular exercise that strengthens the core and hips, such as walking, swimming, Pilates or yoga
• staying active and avoiding long periods of sitting
• maintaining a healthy weight
• warming up before sport or heavy physical work
• staying hydrated in hot weather and during exercise
• managing stress and sleep

Frequently asked questions

What causes lower back spasms?

Most lower back spasms are caused by a muscle strain from lifting, twisting or sudden movement, or by muscles tightening to protect an irritated disc or joint. Prolonged sitting, weak core muscles, dehydration and stress make them more likely. Kidney stones and infections can mimic back spasms.

How long do lower back spasms last?

Most acute back spasms improve significantly within a few days and resolve within 2 weeks. Pain that lasts more than 6 weeks, keeps returning, or comes with leg numbness or weakness should be assessed by a doctor or physical therapist.

Should I use heat or ice for back spasms?

Heat usually works better for muscle spasms because it relaxes tight muscles and increases blood flow. Some people find ice helpful in the first 24 to 48 hours after an injury. Use whichever eases your pain, for 15 to 20 minutes at a time, with a cloth between your skin and the pack.

When is a back spasm an emergency?

Call 911 or go to the ER if back pain comes with numbness in the groin or buttocks, new trouble controlling your bladder or bowels, or rapidly increasing leg weakness. These can be signs of cauda equina syndrome, which needs urgent surgery.

Should I rest in bed with a back spasm?

No. Short rest in a comfortable position for the worst pain is fine, but staying in bed for more than a day or two delays recovery. Gentle walking and gradual return to normal activity help back spasms settle faster.