Back pain when lying flat can come from a poor mattress or spine alignment. Try a pillow under your knees, and see a doctor if it persists.
Common causes
- A mattress that is too soft or firm.
- Poor spinal alignment.
- Muscle strain.
- Herniated disc.
- Arthritis.
- Spinal stenosis.
What helps
- Place a pillow under the knees.
- Side sleeping with a pillow between the knees.
- A medium firm mattress.
- Gentle stretching.
See a doctor
If pain persists, spreads to the legs or comes with numbness.
Emergency
Loss of bladder control. Call 911.
Why lying flat can hurt
Lying flat on a mattress that is too soft or too firm can leave the spine out of neutral alignment. Conditions that hurt more when supine include herniated discs, spinal stenosis, sacroiliac joint dysfunction, ankylosing spondylitis and muscle strain. Inflammatory back pain from ankylosing spondylitis is worse at night and eases with movement.
- About 80 percent of adults experience back pain at some time, according to the NIH.
- Placing a pillow under the knees reduces tension in the lower back for people who lie face up.
- Side sleeping with a pillow between the knees keeps the pelvis aligned.
Care and red flags
Heat, gentle stretching and short walks help. Over-the-counter NSAIDs may help when safe. See a doctor for back pain lasting more than 6 weeks, or with fever, unexplained weight loss, numbness in the groin, loss of bladder or bowel control, or leg weakness. Cauda equina syndrome is an emergency. Back pain with a pulsing abdomen sensation or tearing chest pain can signal aortic issues and needs emergency care.
Why lying flat can hurt
Lying flat may increase pressure on spinal discs, a tight hip flexor, a mattress without support, or conditions such as spinal stenosis, herniated disc, ankylosing spondylitis or kidney problems. Most back pain improves within weeks.
Care and red flags
Try a pillow under the knees, a medium firm mattress and gentle walking. Seek urgent help for numbness in the groin, loss of bladder or bowel control, fever, or pain after trauma. See a doctor if pain lasts over 6 weeks.
Mechanisms and conditions
Lying flat flexes or extends the lumbar spine, stretching tight hip flexors and increasing pressure on inflamed joints. Spondylolisthesis, spinal stenosis and disc problems can hurt more when flat. Kidney stones and pancreatitis cause back pain that worsens lying flat.
What to try
Sleep on your side with a pillow between the knees, or on your back with a pillow under the knees. A medium firm mattress reduced pain in a trial compared with firm. Gentle stretching like knee to chest or cat cow helps. See a doctor if night pain wakes you, with fever or weight loss.
Based on data from the NIH and the American Academy of Orthopaedic Surgeons
