The Side SleeperHow to use a knee pillow (side, back, and without it slipping)
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On your side, it goes between your knees, with your knees slightly bent, so that your top thigh stays level with your hip. On your back, it goes under your knees, not between them.
If it keeps escaping in the night, use a strap, use a longer pillow your whole leg rests on, or check it isn't too thick. An over-tall pillow gets squeezed out.
On your side, step by step
- Lie on your usual side with your head pillow where it normally is. Bend your knees a little, the way you'd naturally curl up.
- Put the pillow between your knees. If it's contoured (hourglass, heart, butterfly), your knees go into the dips on each side. The listing photos show which way up it's meant to go.
- Slide it up or down until your top thigh is level. Seen from the foot of the bed, it should run parallel to the mattress, neither drooping toward your bottom knee nor propped above your hip. If you can't get it level anywhere, the pillow is the wrong height: here's how to find yours.
- Check your feet. If your top foot hangs down off the end of a short pillow, a second small pillow between your ankles helps, or a full-leg pillow does the whole job.
Compact
about 10″ long, at the knee
Long
thigh and knee, 14″
Full-leg
down to the ankle, 26–29″
Above the knee or below it?
Listings disagree, and some say either is fine. Go by the level-thigh check rather than by a rule. Most people end up with the pillow right at the knees, where the gap is easiest to hold. If your knee bones knock against a hard edge, nudge it up a little toward your thighs.
On your back
On your back there's no gap between your knees to fill. Instead, the pillow goes under your knees and lets them bend a little. The NHS suggests exactly this for people with outer-hip pain: "lying on your back with a pillow under your knees".
Most knee pillows are shaped to go between the knees, but some listings say they also work underneath. The 5 STARS UNITED Knee Pillow for Side Sleepers lists four positions, including "beneath the knees for back sleepers". The fibre-filled MINUPWELL Knee Pillow (knee-to-ankle) says you can "shift it between your knees or under them". A regular bed pillow does the under-the-knees job well too.
If you switch between back and side
Taking the pillow with you as you turn soon becomes a habit. If it doesn't, two things help. A strap keeps the pillow on one leg, so it comes along when you roll. A long or full-leg pillow is hard to lose, because your leg is lying on it, not just pinching it.
Strap or no strap?
A strap is an elastic or adjustable band that loops around one leg, so the pillow travels with that leg. Of the 24 knee pillows in the comparison table, 6 come with one, 7 say they don't, and 11 don't say either way.
A strap is worth it if…
- you wake up and the pillow is under the duvet or on the floor
- you turn over a lot in the night
- you're using a compact pillow, which is the easiest kind to lose
Skip it if…
- anything around your leg keeps you awake
- you run hot, since a band is one more thing against your skin
- you use a long or full-leg pillow, which mostly stays put by itself
If you do use one, fasten it snugly but not tightly. You should be able to slide a couple of fingers under it. The Contour Legacy Leg & Knee Pillow listing argues against straps altogether and calls them "circulation restricting", but it gives no evidence for that. A strap that's comfortably loose is a different thing from a tight one.
Check the listing text, not the photo. The main photo for the 5 STARS UNITED Knee Pillow for Side Sleepers shows a blue band, and the listing says no strap is included.
Keeping it in place without a strap
- Get the height right. A pillow that's too thick for your knee gap is squeezed from both sides all night, and it tends to pop out. The towel test takes five minutes.
- Go longer. Long and full-leg pillows rest along your leg, so there's more of you holding them down.
- Look for raised edges or a seam. The ComfyInLove Heart-Shaped Knee Pillow uses raised edges instead of a strap. The MINUPWELL Knee Pillow (knee-to-ankle) has a seam down the middle that's meant to keep it from sliding.
- Mind the fabric. A shiny cover against silky pyjamas slides more easily than cotton against cotton. If yours keeps escaping, that's a cheap thing to change.
Quick answers
Does a knee pillow go above or below the knee?
At the knees, for most people. Go by your top thigh rather than a rule: slide the pillow up or down until the thigh runs level with the mattress. If your knee bones knock against a hard edge, nudge it a little up toward your thighs.
Do you need a strap on a knee pillow?
Only if the pillow keeps escaping in the night. 6 of the 24 best-selling knee pillows come with one, 7 have none and 11 don't say. Fasten it loosely enough to slide a couple of fingers under it.
Where does a knee pillow go when you sleep on your back?
Under your knees, not between them, so your knees bend a little. The NHS suggests lying on your back with a pillow under your knees for outer-hip pain. Some knee pillows are shaped to work both ways, and a regular bed pillow does the job too.
Should you put a pillow between your ankles too?
If your top foot sags off the end of a compact pillow, yes. Tuck a small second pillow between your ankles, or use a full-leg pillow, which runs 26 to 29 inches down to the ankle among the best sellers.
Sources
- Back and side positions with a pillow: Greater trochanteric pain syndrome, NHS inform.
- Straps, positions and quoted claims: Amazon US listing text, collected October 5, 2026. Every pillow's strap status is in knee pillows compared.