The short answer: Side sleepers: a pillow between the knees keeps the top leg from dragging the pelvis round. The 5 STARS UNITED is the most-reviewed one we found; the NATUMAX has a strap if you turn a lot; the Lofe runs knee to thigh for wider hips. Back sleepers: a wedge under the knees takes the arch out of the lower back. The Bedluxe is the firmer wedge, the RUQMUIS the softer one.
Top knee pillows for back pain
- 15 STARS UNITED Knee PillowBest knee pillow for side sleepers
- 2Bedluxe Knee Wedge PillowBest knee wedge for back sleepers
- 3NATUMAX Knee Pillow with Leg StrapBest if you turn over a lot
- 4Lofe Adjustable Full-Leg Knee Pillow (4 in)Best full-length pillow for wider hips
- 5RUQMUIS 8 in Knee Wedge PillowBest soft knee wedge
Why a pillow at the knees changes how your back feels
Lie on your side with nothing between your legs and the top knee drops toward the mattress. It takes the hip with it, the pelvis rotates forward, and the lower back is held in a gentle twist for hours. A pillow about as thick as the gap between your knees stops that drop, so the spine stays closer to straight. It is the same reason physiotherapists so often suggest it before anything more expensive.
On your back the problem is different. With the legs flat, the muscles at the front of the hips pull the lower back into an arch. Raise the knees a little and that pull eases, which is why a wedge or a rolled pillow under the knees helps many back sleepers wake with less stiffness.
Neither fixes a sagging mattress or a medical problem, but both are cheap to try and easy to return. If you are about to replace a bed, try the right pillow for a week first; it tells you whether alignment, not firmness, is what has been hurting.
5 STARS UNITED Knee Pillow
The most-reviewed knee pillow in our collection: a contoured memory foam block that sits between the knees.
Why it is here: A contoured memory foam block about six inches tall, sold by the brand and shipped by Amazon, with by far the most owner reviews of any knee pillow we collected. The cover comes off for the wash.
- Sold by the brand itself
- Shipped by Amazon
Scale: our reading of the maker's label.
- Build
- Contoured memory foam, 9.8 x 7.8 x 6 in, washable knit cover, no strap
- Warranty
- Not stated on listing
- Sold by
- 5 STARS UNITED (the brand)
- Price band
- Budget
Good fit if
You sleep on your side, wake with a sore lower back or hip, and want the simplest, cheapest thing to try first.Look elsewhere if
You turn over a lot at night; there is no strap, so it can end up on the floor.Other versions: Large
Bedluxe Knee Wedge Pillow
A memory foam wedge that keeps the knees bent while you sleep on your back.
Why it is here: A medium-firm memory foam wedge, CertiPUR-US certified, that holds the knees bent all night. The maker says it suits people 5 ft 3 in and taller.
- Sold by the brand itself
- Shipped by Amazon
Scale: our reading of the maker's label.
- Build
- CertiPUR-US memory foam wedge, 23.6 x 18.9 x 7.9 in, removable knitted cover
- Warranty
- Not stated on listing
- Sold by
- Bedluxe (the brand)
- Price band
- Budget
Good fit if
You sleep on your back and your lower back aches when your legs lie flat.Look elsewhere if
You are under about 5 ft 3 in; the maker says it may be too large for you.
NATUMAX Knee Pillow with Leg Strap
A knee pillow with a strap, so it stays between your legs when you roll from one side to the other.
Why it is here: An elastic strap holds it to one leg, so it comes with you when you roll over instead of ending up under the duvet. Medium soft, with a zippered cover.
- Sold by the brand itself
- Shipped by Amazon
Scale: our reading of the maker's label.
- Build
- Memory foam, 9.45 x 6.5 in, zippered washable cover, elastic leg strap; ships with a sleep mask and earplugs
- Warranty
- Not stated on listing
- Sold by
- Rumal (named on the listing as manufacturer)
- Price band
- Budget
Good fit if
You change sides several times a night and keep losing an ordinary knee pillow.Look elsewhere if
You find straps fiddly or warm; the strapless 5 STARS UNITED is the simpler choice.
Lofe Adjustable Full-Leg Knee Pillow (4 in)
A long, adjustable pillow that runs from knee to thigh, with a 1-inch layer you can take out to change the height.
Why it is here: Twenty-six inches long and adjustable: take out the 1-inch insert to drop the height from four inches to three. Longer pillows keep the thigh, knee and ankle in line, not just the knees.
- Sold by the brand itself
- Shipped by Amazon
Scale: our reading of the maker's label.
- Build
- Memory foam in two layers (3 in plus a removable 1 in insert), 26 x 13 x 4 in, cooling removable case
- Warranty
- Not stated on listing
- Sold by
- Lofe (the brand)
- Price band
- Budget
Good fit if
You have wider hips, or a short knee pillow leaves your thighs and ankles out of line.Look elsewhere if
You want something small enough to pack for travel.
RUQMUIS 8 in Knee Wedge Pillow
A softer knee wedge with a machine-washable, OEKO-TEX certified cover.
Why it is here: The same footprint as the Bedluxe in a softer foam, with an OEKO-TEX Standard 100 cover that goes in the washing machine.
- Sold by the brand itself
- Shipped by Amazon
Scale: our reading of the maker's label.
- Build
- CertiPUR-US foam wedge, 23.6 x 18.9 x 7.9 in, OEKO-TEX Standard 100 cover, machine-washable
- Warranty
- Not stated on listing
- Sold by
- RUQMUIS (the brand)
- Price band
- Budget
Good fit if
You want knee elevation for back sleeping but find firm wedges hard under the calves.Look elsewhere if
You want firm, steady support under the knees; the Bedluxe is the firmer of the two.
Knee pillows picks, spec by spec
| Model | Firmness | Build | Zoned | Trial | Warranty | Sold by |
|---|---|---|---|---|---|---|
| 5 STARS UNITED Knee Pillow | 3–4/10 | Contoured memory foam | — | — | Not stated on listing | 5 STARS UNITED |
| Bedluxe Knee Wedge Pillow | 6–7/10 | CertiPUR-US memory foam wedge | — | — | Not stated on listing | Bedluxe |
| NATUMAX Knee Pillow with Leg Strap | 4–5/10 | Memory foam | — | — | Not stated on listing | Rumal |
| Lofe Adjustable Full-Leg Knee Pillow (4 in) | 5–6/10 | Memory foam in two layers (3 in plus a removable 1 in insert) | — | — | Not stated on listing | Lofe |
| RUQMUIS 8 in Knee Wedge Pillow | 3–4/10 | CertiPUR-US foam wedge | — | — | Not stated on listing | RUQMUIS |
"Not stated on listing" means the Amazon page we read did not say. Ask the seller before you rely on it.
Between the knees or under them?
- Side sleepers want a pillow between the knees, roughly as thick as the distance from the mattress to your top knee. For most adults that lands around five to seven inches.
- Back sleepers want a wedge or bolster under the knees, enough to bend them slightly without lifting the hips.
- People who switch often do best with a side-sleeper pillow that can also sit under the knees; the 5 STARS UNITED listing names both uses.
Size, height and the strap question
Height matters more than foam. Too thin and the top knee still drops; too thick and the hip is pushed up instead. Wider hips usually need a taller or longer pillow, which is where full-length designs like the Lofe earn their place. A strap is worth having if you change sides several times a night; if you sleep fairly still it is one more thing to adjust.
When a pillow is not enough
If you wake sore whatever you put between your knees, the mattress itself may be the issue: see our picks for side sleepers with back pain or back sleepers. A lumbar pillow fills a different gap, the one under the small of the back. And pain that runs down a leg, or comes with numbness or weakness, is a reason to see a clinician rather than to shop.
Before you order: reader questions
Does a knee pillow help lower back pain?
For many side sleepers, yes: it stops the top leg from rotating the pelvis, which keeps the lower back from twisting overnight. Back sleepers get a similar benefit from a wedge under the knees. It will not fix a sagging mattress.
How thick should a knee pillow be?
Roughly the gap between your knees when you lie on your side with your hips stacked, usually five to seven inches for adults. Wider hips need a taller or longer pillow.
Should I put a pillow under my knees if I sleep on my back?
Many back sleepers find it eases lower back stiffness, because bending the knees slightly relaxes the pull on the lower back. A purpose-made wedge stays in place better than a bed pillow.
Is a knee pillow good for sciatica?
It can make side sleeping more comfortable by keeping the pelvis level. Sciatica that is severe, getting worse, or comes with numbness or weakness should be checked by a clinician first.
Neutral Spine is not a medical provider. A mattress can make sleep more comfortable; it does not treat a spinal condition. Pain that follows an injury, spreads down a leg, or comes with numbness, weakness or fever needs a doctor first. Full disclaimer.