Side sleeper knee pillow: keep your hips stacked through the night
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- Contoured hourglass knee pillow with leg strap. Best for: Most side sleepers, especially those who lose the pillow overnight. See options on Amazon
- Wide knee pillow for larger frames. Best for: Broad hips or long legs. See options on Amazon
- Full-length knee-to-ankle pillow. Best for: Side sleepers whose ankles or calves also press together. See options on Amazon
- Long body pillow. Best for: Restless sleepers and people who like to hug a pillow. See options on Amazon
What a knee pillow does for side sleepers
The Sleep Foundation explains that a major problem with side sleeping is the upper leg collapsing onto the lower leg, which twists the spine. A pillow between the knees helps keep the spine in a more natural, neutral position, keeps the legs aligned and stops the hips from twisting. It also cushions the knees where one bony joint would otherwise press into the other.
Mayo Clinic's advice for back pain is simple: draw your legs up slightly toward your chest and put a pillow between your legs. A full-length body pillow is another option it mentions.
Knee pillow shapes compared
| Shape | Best for | Trade-off |
|---|---|---|
| Hourglass or contoured | Most side sleepers; cups both knees | Can slip away when you turn over |
| Wedge | Wider, firmer separation | Feels bulky between the knees for smaller sleepers |
| Cylinder or bolster | Simple, rolls with you | Less stable; knees can slide off |
| Full-length knee-to-ankle | Supports knees, calves and ankles together | Takes more space and is harder to reposition |
| Body pillow | Hugging, frequent position changes, pregnancy | Takes up a lot of bed |
The Sleep Foundation notes most knee pillows have a contoured or hourglass shape, with wedge and cylinder shapes as other options, and that some are long enough to support the calves and ankles.
Getting the size right
- Thickness: the Sleep Foundation says the pillow should be snug enough to stay in place but not so thick that it widens the gap between your legs too much. The aim is to keep your top knee roughly level with your top hip.
- Width: larger sleepers may prefer a wider pillow for more coverage, while smaller sleepers may prefer a compact one.
- Firmness: there is no single right answer. Firmer pillows hold their shape; softer ones mold to the knees.
- Strap: an elastic leg strap helps if you wake up and find the pillow on the floor.
- Cover: a removable, washable cover in breathable fabric such as cotton or a bamboo-derived blend.
Comparing foam types? Our memory foam knee pillow guide covers density, heat and odor.
How to use it
- Lie on your side and bend your knees slightly. The Sleep Foundation says most people find a slight bend more natural and supportive.
- Place the pillow between your knees, with the narrow middle of an hourglass shape between the joints.
- Check that your top knee is not higher or lower than your top hip.
- If your ankles touch or your feet ache, use a longer pillow that supports the calves and ankles too.
- If you switch sides often, try a body pillow or a longer knee pillow, which the Sleep Foundation suggests for people who move a lot.
Before buying anything, you can test the idea by folding a regular pillow in half between your knees, a do-it-yourself option the Sleep Foundation mentions.
Pairing it with the rest of your setup
A knee pillow fixes the hips but not the neck or shoulders. The Sleep Foundation notes that shoulders and hips bear most of your weight on your side, so a mattress that is too firm can still leave pressure points. See our guides to the pillow for side sleepers with neck pain and mattress topper for side sleepers.
What to look for when you buy
Contoured hourglass knee pillow with leg strap
Best for: Most side sleepers, especially those who lose the pillow overnight
The contoured shape cups both knees, and a strap keeps it in place so the top leg does not drop and twist the spine.
Watch out: Straps can feel restrictive if you change sides often.
See options on AmazonWide knee pillow for larger frames
Best for: Broad hips or long legs
The Sleep Foundation notes larger sleepers may prefer a wider pillow for more coverage, which helps keep the top knee level with the hip.
Watch out: Too thick for smaller sleepers and can push the knees too far apart.
See options on AmazonFull-length knee-to-ankle pillow
Best for: Side sleepers whose ankles or calves also press together
Supports the knees, calves and ankles together, so the whole top leg stays parallel to the bottom one.
Watch out: Bulkier and harder to move when you turn over.
See options on AmazonLong body pillow
Best for: Restless sleepers and people who like to hug a pillow
Mayo Clinic mentions a full-length body pillow as an option for side sleepers, and it supports the arms as well as the knees.
Watch out: Takes up a lot of bed space and can be warm.
See options on AmazonQuestions people ask
- Should side sleepers use a knee pillow?
- Many find it helps. A pillow between the knees keeps the top leg from dropping and twisting the hips and lower back.
- How thick should a knee pillow be?
- Thick enough to keep your top knee level with your top hip, and no thicker. Too much height pushes the legs apart.
- Can I just use a regular pillow between my knees?
- Yes. The Sleep Foundation says folding a standard pillow in half can give enough loft, and it is a good way to test the idea.
- Is a knee pillow good for hip pain?
- It may help by keeping the legs aligned and reducing twisting at the pelvis. Ongoing hip pain should still be checked by a clinician.
Sources
- Sleeping With a Pillow Between Your Knees (www.sleepfoundation.org/best-pillows/sleeping-with-a-pillow-between-your-knees), Sleep Foundation
- Sleeping positions that reduce back pain (mayoclinic.org), Mayo Clinic
- Side Sleeping: Which Side Should You Sleep On? (www.sleepfoundation.org/sleeping-positions/side-sleeping), Sleep Foundation