Under Knee Pillow for Sleeping on Back: 5 Best (2026)

2026 buying guide · back-sleeping comfort & knee support

An under knee pillow for sleeping on your back should support both knees and create a gentle bend without forcing your hips or legs into an uncomfortable angle. For most people, a wide half-moon bolster is the simplest option; an adjustable pillow suits uncertain height needs, while a full leg wedge provides substantially more elevation.

Quick picks

Does sleeping with a pillow under your knees help your back?

It can make back sleeping more comfortable for some people. Mayo Clinic says placing a pillow under the knees may help relax the back muscles and maintain the curve of the lower back. NIAMS, part of the NIH, also recommends a pillow under the knees for people who tend to sleep on their backs.

A specialty pillow is optional. The medical guidance says to use a pillow under the knees; it does not say you need a specific brand or shape. Before buying anything, try a regular pillow for a few nights. If the position helps but your pillow flattens, shifts, or feels too bulky, a dedicated bolster may be more convenient.

How we chose these under-knee pillows

We treated this as a back-sleeping problem, not a generic “knee pillow” roundup. We prioritized products wide enough to support both knees, shapes that make sense under the legs, useful height or firmness differences, removable covers, and current U.S. Amazon listings. We excluded hourglass pillows designed mainly to sit between the knees of side sleepers.

This is a specification-based editorial comparison. Category labels such as “best overall” are our judgment about design and use-case fit, not results from a laboratory test or head-to-head clinical trial. Prices, sellers, variants, and stock change; check the current Amazon listing before ordering.

Best under-knee pillows for back sleepers at a glance

On a small screen, swipe the table sideways. The exact dimensions and available variants should be rechecked on the listing before purchase.

Back sleeper vs. side sleeper: An hourglass pillow that wedges between the knees is designed for a different position. For back sleeping, look for a bolster or wedge that can support both legs at once without pushing the knees apart.

The five product profiles

How do you use an under-knee pillow when sleeping on your back?

Place the pillow beneath both knees so they bend gently while your hips, pelvis, and lower back remain comfortable. The pillow does not need to force a dramatic angle. Your head pillow should also keep your neck aligned with your chest and back. Adjust the support based on comfort rather than chasing a universal “correct” height.

1. Start with a low-risk test. Try a normal pillow under both knees before buying a specialty product. Notice whether the position makes your back and hips feel more relaxed.
2. Center the support. Put the bolster under both knees, not under only one leg. A larger wedge may extend under the calves as designed.
3. Look for a gentle bend. Your knees should feel supported rather than sharply flexed. Move the pillow slightly toward your thighs or calves if the pressure point feels awkward.
4. Recheck your head and neck. Mayo Clinic advises supporting the neck so it stays aligned with the chest and back. If your head pillow is too high or too low, fixing only the knees may not make the whole position comfortable.
5. Stop if symptoms worsen. A pillow should not cause new pain, tingling, numbness, weakness, skin pressure, or a feeling that your joints are being forced into position.

For head-and-neck support options, see our pillow guide for neck and shoulder pain.

What should you look for in an under-knee pillow?

The most important factors are shape, height, usable width, firmness, and whether the pillow stays comfortable on your mattress. A good choice supports both legs without making you feel trapped in one exact position. Because bodies and mattresses differ, dimensions are more useful than marketing terms such as “orthopedic” or “pain-relief” when comparing products.

Half-moon bolster or full leg wedge?

A half-moon bolster creates a focused bend beneath the knees and uses relatively little bed space. A leg wedge supports a longer section of the lower legs and usually creates more elevation. Neither design is automatically healthier. Choose the one that feels comfortable and matches any medical instructions you have been given.

How much height do you need?

There is no evidence-based universal pillow height for every back sleeper. In this shortlist, the bolsters are around four to five inches high, while the DMI wedge is much taller. If you are unsure, an adjustable design or a regular pillow trial is a safer way to learn what feels comfortable before committing to a fixed profile.

Check the usable width

The pillow needs enough side-to-side room for your normal leg position. A 20- or 21-inch bolster gives more room for the knees to drift apart than a compact 17-inch model. Measure the space your legs naturally occupy when you lie on your back rather than assuming a smaller pillow will stay under both knees.

Firmness and foam feel

Very soft fill may compress until the knee bend disappears, while very firm foam can create an uncomfortable pressure point. Memory foam changes feel with temperature and body weight, so a brand’s generic “soft” or “firm” label is not a standardized clinical measure. A good return policy is useful if you cannot test the pillow first.

Cover and cleaning

A removable, washable cover is practical for something used nightly. Follow the care instructions for the exact model; memory-foam cores generally should not be machine washed just because the cover can be. Also check whether replacement covers are available if that matters to you.

Don’t shop by medical-sounding words alone. “Orthopedic,” “sciatica,” or “pain relief” in a product title does not prove a pillow treats a condition. Compare dimensions and construction first, then use medical guidance—not marketing copy—to decide whether changing your sleep position makes sense.

Is back sleeping with a knee pillow right for everyone?

No. Although under-knee support is commonly suggested for comfortable back positioning, the sleeping position itself is not ideal for everyone. The NHS lists sleeping on the back as a factor linked with obstructive sleep apnoea and advises people diagnosed with sleep apnoea to sleep on their side.

When should you see a healthcare professional for back pain?

Get medical advice when back pain lasts more than a few weeks, is severe and does not improve with rest, spreads down a leg, or comes with weakness, numbness, or tingling. Seek immediate care for new bowel or bladder problems, fever with back pain, or pain after a significant fall or other injury. These are not pillow-fit problems.

Mayo Clinic’s back-pain guidance and NIAMS provide fuller lists of symptoms that warrant assessment.

Positioning aid, not treatment. An under-knee pillow may make a sleeping position more comfortable, but it does not diagnose or cure sciatica, arthritis, disc problems, circulation disorders, or other causes of pain. If a clinician has given you post-operative or condition-specific positioning instructions, those instructions take priority.

If lying flat is difficult and you are comparing other sleep/rest positions, our recliner for back pain guide covers a different support approach.

Frequently asked questions

Does putting a pillow under your knees help when sleeping on your back?

It can make back sleeping more comfortable for some people. Mayo Clinic says a pillow under the knees may help relax the back muscles and maintain the natural curve of the lower back. It is a positioning aid, not a treatment for the underlying cause of persistent back pain.

How high should an under-knee pillow be?

There is no single ideal height for everyone. The goal is a gentle knee bend that feels comfortable without forcing the hips or knees into an awkward angle. Start with a modest bolster, then adjust the height or position. If a pillow increases pain, numbness, tingling, or pressure, stop using it.

Is a half-moon pillow or a leg wedge better for back sleeping?

A half-moon bolster is usually simpler when you only want support directly under both knees. A larger leg wedge supports more of the calves and can create greater elevation, but it also takes more bed space. Choose the shape that produces a comfortable position rather than assuming more elevation is better.

Can I use a regular pillow under my knees instead?

Yes. Medical guidance generally says to place a pillow under the knees; it does not require a specialty product. A regular pillow is a sensible way to test whether the position feels better. A shaped bolster mainly adds predictable height, firmness, and a design that may shift less during the night.

Can an under-knee pillow cure sciatica or lower-back pain?

No pillow should be presented as a cure for sciatica or back pain. Knee support may change your sleeping position and improve comfort, but radiating pain can have several causes. Seek medical advice if pain is persistent, severe, worsening, or accompanied by weakness, numbness, or other concerning symptoms.

Is back sleeping with a knee pillow suitable if I have sleep apnoea?

Not always. The NHS notes that sleeping on your back is linked with obstructive sleep apnoea and advises people diagnosed with sleep apnoea to sleep on their side. If you have sleep apnoea, loud snoring, witnessed breathing pauses, or marked daytime sleepiness, discuss sleep position with a healthcare professional.

This article is for general information only and is not medical advice. Talk to a qualified healthcare professional about your specific symptoms, diagnosis, sleep position, and recovery plan.