Knee Pillow for Side Sleepers: Shapes, Sizing and How to Use One
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Calm Eden Sleep Journal · Updated October 4, 2026
A knee pillow for side sleepers goes between your knees so your top leg stays level with your hip instead of dropping forward. Most adults suit a contoured memory foam pillow about 10–15 cm (4–6 in) thick with a strap; choose a body pillow if you also like to hug one.
When you lie on your side with nothing between your legs, your top knee slides forward and down toward the mattress. That turns the pelvis and twists the lower back, and the position can feel lopsided by morning. A knee pillow fills the gap between your legs so the top leg stays parallel to the bottom one.
What a knee pillow does (and doesn't do)
- Keeps the knees apart so they don't press bone-on-bone.
- Levels the top leg so the hips and lower back stay stacked instead of rotating.
- Reduces tossing for some people, because the position feels more stable.
It is a comfort aid. If you have hip or back pain that is severe, getting worse, or comes with numbness or weakness, have it assessed rather than relying on a pillow.
Shapes compared
| Shape | How it feels | Best for |
|---|---|---|
| Contoured / hourglass | Curved cut-outs cradle each knee | Most side sleepers; stays in place well |
| Rectangular or wedge | Flat, even support; sometimes tapered | People who shift the pillow down to the calves |
| Half-moon / under-knee | Round roll under bent knees | Back sleepers who want the knees slightly raised |
| Full-length body pillow | Supports arms, hips, knees and ankles | Side sleepers who like to hug something; pregnancy (ask your provider) |
How thick should a knee pillow be?
The pillow should hold your top knee at about the same height as your top hip. People with wider hips relative to their knees need a thicker pillow; slimmer builds need less. As a rough guide:
- 8–10 cm (3–4 in): slimmer builds, softer mattresses.
- 10–15 cm (4–6 in): most adults.
- 15 cm+ (6 in+): wider hips or a firm mattress.
Too thick is as uncomfortable as too thin — it pushes the top leg up and opens the hip. Memory foam compresses a little under the weight of your leg, so a contoured 12–14 cm pillow often feels closer to 10 cm in use.
How to use a knee pillow
- Lie on your side and bend your knees slightly, as if sitting in a chair.
- Place the pillow between your knees, with the thicker part toward the front if it's tapered.
- Let your ankles rest together or on the lower edge — some people prefer the pillow long enough to support the ankles as well.
- Fasten the strap (if it has one) around the top leg so it follows you when you turn.
- Combine it with a head pillow at the right height — see our side-sleeper pillow height guide — so your spine is level from neck to hips.
Pair it with the right head pillow. The knee pillow looks after your legs; your head pillow fills the gap between your neck and the mattress. The two-sided Amity Comfort Cervical Pillow has a contoured face and a hollow face with an armrest area for side sleeping, so you can try both on your own mattress.
Knee pillow vs body pillow
A knee pillow is compact, easy to travel with and doesn't take over the bed. A body pillow does the same leg job but also gives your top arm somewhere to rest, which stops you rolling forward onto your stomach. If you already hug a spare pillow at night, a body pillow is usually the more comfortable upgrade; if space is tight, stick to a knee pillow.
Knee and body pillows we stock
From our side-sleeper collection:
| Pillow | Type | Listed size | Listing facts | Price (checked October 4, 2026) |
|---|---|---|---|---|
| Poise Memory Foam Knee Pillow | Contoured knee pillow | Not stated on the listing | Contoured memory foam; adjustable strap; removable, washable cover | $48.90 |
| Selene Side Sleeper Knee Pillow | Hourglass knee pillow | 15 cm thick | 50D memory foam with a contoured center; adjustable thigh strap | $39.90 |
| Hammock Ergonomic Knee Pillow | Contoured knee pillow | 25 × 20 × 15 cm | Memory foam; adjustable elastic strap; cover unzips for washing | $39.90 |
| Embrace Side Sleeper Body Pillow | Dual-wave body pillow | 47 × 14 in | Lower curve wraps between the legs; four support zones; Blue, Pink, Gray or Sage Green | $59.90 |
| Solstice Cooling Body Pillow | Cooling dual-wave body pillow | 44 × 14 in | Three support zones; works on either side; six colours | $49.90 |
Facts come from each product listing. Poise does not state a size; none of the five listings states a firmness rating. We have not lab-tested these pillows.
Reading the table: Selene and Hammock both list 15 cm, the top of the 10–15 cm range, so they suit wider hips or a firmer mattress; all three knee pillows have a strap to keep them on your leg when you turn. Embrace and Solstice do the leg job and give your top arm somewhere to rest; Embrace is the longer of the two.
Every Calm Eden pillow comes with a 30-day risk-free trial from delivery. Opened and used pillows are accepted, original packaging is not required and there is no restocking fee. Change-of-mind return shipping is the customer's cost; cancellation is free before the order ships. See the refund policy for the full terms.
Care
Choose a removable, washable cover — a knee pillow sits against bare skin all night. Air the foam core now and then, and replace the pillow when it stays compressed or no longer springs back.
Frequently asked questions
Do knee pillows actually help side sleepers?
Many side sleepers find them more comfortable because the top leg stays level with the hip instead of dropping forward, which reduces twisting through the lower back. Comfort varies, so give it a week.
Where should a knee pillow go?
Between the knees when you sleep on your side, with your knees slightly bent. Back sleepers can put it under the knees instead.
How thick should a knee pillow be?
Thick enough to hold your top knee level with your top hip — about 10–15 cm (4–6 in) for most adults, more for wider hips.
Is a body pillow better than a knee pillow?
It depends on your space and habits. A body pillow supports your arm as well as your legs and suits people who hug a pillow; a knee pillow is smaller and easier to keep in place.
Can I use a knee pillow during pregnancy?
Many people use knee or body pillows for side sleeping during pregnancy. Ask your midwife or doctor about the position and support that's right for you.
Should a knee pillow go between the knees or the ankles?
Between the knees for most side sleepers, with the knees slightly bent. If your ankles press together or your lower leg feels unsupported, slide it a little lower or choose a longer pillow or body pillow that reaches the ankles.
Do I still need a head pillow with a knee pillow?
Yes. A knee pillow supports your legs; a head pillow fills the gap between your neck and the mattress. Choose the head pillow height for your shoulder width and mattress feel.
Can I return a knee pillow after using it?
Yes. Calm Eden pillows come with a 30-day risk-free trial from delivery, and opened and used pillows are accepted. Change-of-mind return shipping is the customer's cost; see the refund policy for the full terms.
Keep reading
- Shop side-sleeper pillows
- Pillow height for side sleepers
- Body pillows for side sleepers
- Pregnancy pillow shapes
- Wedge pillow guide
- Cervical pillow guide
Calm Eden sells some of the products mentioned here. Product details come from our own listings; we have not lab-tested them, and comfort varies from person to person. This guide is general information, not medical advice — if you have ongoing pain, numbness, breathing problems at night or a diagnosed condition, talk to a clinician before changing how you sleep.