The Side Sleeper
Knee pillow guides · Buying

Knee pillow shapes, explained

Nell, the Side Sleeper
Updated · Data collected · How we research

Shape decides two things: how your knees sit on the pillow, and how much of your leg it holds. Hourglass, heart and wedge pillows are compact and sit at the knee. Long and full-leg pillows run down the thigh or all the way to the ankle.

Height matters more than shape, so find your number first. Then use shape to choose between pillows of the right height.

The 24 knee pillows in the comparison table, grouped by shape. Best sellers on Amazon US plus two brands that sell direct, collected October 5, 2026.

19 of the 24 are compact pillows that sit between the knees, and 14 of those are the three familiar shapes: hourglass, heart and contoured wedge. Everything else is a variation on one of two ideas: a pillow you can set to your own height, or one long enough that your leg lies along it.

How a shape holds your knees

Look at a knee pillow end-on, the way you'd see it from the foot of the bed, and the compact ones fall into two kinds. Some have flat faces, and your knee rests on top. Others have a shallow dip on each face, and your knee settles into it.

Flat faces: Straighter shapes, like the I-shape. The gap at your knees is close to the listed height. listed height gap

Flat faces
Straighter shapes, like the I-shape. The gap at your knees is close to the listed height.

Dipped faces: Hourglass, heart. Each knee sits in a dip, so the gap is less than the listed height. listed height gap

Dipped faces
Hourglass, heart. Each knee sits in a dip, so the gap is less than the listed height.

Seen from the foot of the bed, lying on your side. The circles are your knees and the dashed line is the gap the pillow holds them apart. Both pillows have the same listed height. The drawing is to illustrate the idea, not to scale: no listing gives the depth of its dips.

Dips do two useful things. They stop your knees sliding off the sides, and they hold the pillow in one place along your leg. The cost is that a dipped pillow holds your knees closer together than its listed height suggests, because that height is measured at the outside edges. So if your towel test says 6 inches, a dipped pillow listed at 6 inches will sit a bit low. Lean slightly taller.

Each shape, and what it's for

Hourglass

6 pillows · 9.85–10.4″ long · 5.7–6.9″ thick · 2 with a strap

The classic, and the most common shape among the best sellers. Both faces dip in the middle, so the pillow pinches in at the waist like an hourglass and each knee sits in its own dip. Contour, maker of the #1 best seller, the Contour Legacy Leg & Knee Pillow, says it invented the shape in the early 1990s, and that the shape holds the pillow in place without a strap. Some go further: the UJPFEO Knee Pillow with Dual Inner Grooves adds grooves meant to keep your thighs apart as well as your knees.

Suits: most side sleepers. It's the default, with the most choice.

Heart

3 pillows · 10–11.02″ long · 5–7.2″ thick · 1 with a strap

A rounder, bigger cousin of the hourglass. The heart pillows are among the biggest compact knee pillows in the table, 10–11.02″ long, and the tallest fixed-height ones: two of the three are 7.2″, taller than any fixed-height hourglass or wedge. The ComfyInLove Heart-Shaped Knee Pillow uses "gently raised edges" instead of a strap to stay put. The TULARIS Heart Knee Pillow with Adjustable Strap is the exception at 5″, and it comes with a strap.

Suits: wide hips, a high towel-test number, or anyone who finds the standard sizes too small.

Contoured wedge

5 pillows · 9.5–10.6″ long · 5.5–6″ thick · 1 with a strap

A block shaped to fill the gap between your legs. The listings describe the foam as contouring to the knees, legs and thighs rather than giving each knee a dip. Wedges tend to be the most versatile: the 5 STARS UNITED Knee Pillow for Side Sleepers lists four positions, including between your calves and under your knees when you lie on your back. The Cushion Lab Side Sleeper Knee Pillow, sold direct, is the same idea in extra-dense foam.

Suits: people who switch between side and back and want one pillow for both. Check the listing photos for which way up it goes.

Butterfly

1 pillow · 9.45″ long · thickness not given · 1 with a strap

Named for its outline, with rounded wings either side. The one best seller in this shape, the NATUMAX Knee Pillow + Sleep Mask + Ear Plugs, says it can go above or below the knees. It doesn't give its thickness, so you'd be buying the height blind.

I-shape

1 pillow · thickness not given · no straps

Squarer than an hourglass, with straighter faces, so the gap at your knees is closer to the listed height. The catch is that the one in the table, the Vaunn Medical Cloud Air Knee Pillow, gives two sets of dimensions that disagree, so you can't tell its height from the listing.

Soft cushion and round

1 pillow · 11″ long · thickness not given · no straps · 1 pillow · thickness not given · no straps

A small, soft, fibre-filled cushion like the HapiPoppy Soft Small Knee Pillow 11" x 7.8" squashes to fit, which makes it gentle but hard to rely on for a set height. It does have a pocket for an ice or heat pack. Round (bolster) pillows are rare among the best sellers. The only one, the BAYANKALA (Revoget) Revoget Alignment Pillow, has a listing too unreliable to judge: it gives impossible dimensions and contradicts itself on the filling.

Adjustable (inserts)

1 pillow · 12″ long · 5–8″ thick · no straps

Not a shape so much as a fix for not knowing your height. The Coop Home Goods Adjustable Knee Pillow comes with removable 1″ and 2″ foam layers, which by my arithmetic lets you set it anywhere from 5″ to 8″ in 1″ steps.

Suits: anyone whose towel test landed between sizes, or above 7 inches.

Long (thigh + knee)

2 pillows · 11–14″ long · 3″ thick · no straps

Longer pillows that cover the thigh as well as the knee. Your leg's weight is spread along them, so they can be thinner: the ROKAFU Knee Pillow 11" (thigh + knee) is 3″. The anzhixiu Long Knee Pillow 14" describes a "semi-circular contour" that cradles the thighs, though its listing gives both 3″ and 5″ for the height.

Suits: a smaller gap, under about 4 inches.

Full-leg

3 pillows · 26–29″ long · 3–6.5″ thick · 1 with a strap

Runs from the knee to the ankle, or from the hip. Because your whole lower leg lies on it, it's the hardest kind to lose in the night, and your top foot can't drop. They differ more than the name suggests: the MINUPWELL Knee Pillow (knee-to-ankle) is fibre-filled with a centre seam (3″), the HOMBYS Shredded Memory Foam Knee Pillow 6.5" is shredded foam that settles under your leg (6.5″ new), and the Xtra-Comfort (Vive Health) Full Knee Pillow 29" runs 29″ from hip to ankle with cutouts so your knees can bend.

Suits: anyone whose top foot hangs down, or whose compact pillow keeps ending up on the floor.

Shapes by the numbers

Shape Pillows Length Listed thickness Strap included Typical price
Hourglass 6 9.85–10.4″ 5.7–6.9″3 of 6 state it 2 of 6 $29
Heart 3 10–11.02″ 5–7.2″ 1 of 3 $36
Contoured wedge 5 9.5–10.6″ 5.5–6″3 of 5 state it 1 of 5 $30
Butterfly 1 9.45″ not given 1 of 1 $36
I-shape 1 not given not given 0 of 1 $25
Soft cushion 1 11″ not given 0 of 1 $36
Round 1 not given not given 0 of 1 $30
Adjustable (inserts) 1 12″ 5–8″ 0 of 1 $45
Long (thigh + knee) 2 11–14″ 3″1 of 2 state it 0 of 2 $38
Full-leg 3 26–29″ 3–6.5″ 1 of 3 $36

Ranges cover the listings that give each number; thickness counts only clearly stated values (the adjustable pillow's range is worked out from its inserts). Typical price is the median, from October 5, 2026. Prices change daily. Every pillow, with its source: knee pillows compared.

Which shape for you

Your number is about 5 to 7 inches

Hourglass or contoured wedge. That's where most of the choice is. Pick by listed height, then lean slightly taller for a dipped one.

Your number is over 7 inches

A heart shape, or the adjustable pillow. Among pillows that state their height, those are the only compact ones that go that tall.

Your number is under 4 inches

A long or full-leg pillow. Most are thinner than compact ones, because your leg's weight is spread along them.

It keeps escaping, or your foot drops

Full-leg. If you'd rather stay compact, choose one with a strap (strap or no strap).

If you'd like your arm and shoulder held up too, you may want a body pillow instead: knee pillow vs body pillow.

Quick answers

What is the best shape for a knee pillow?

There isn’t one best shape, only a best height for your knees. Hourglass and contoured-wedge pillows are the most common and suit most side sleepers. Heart shapes run bigger and taller. Long and full-leg pillows suit you if your foot drops or the pillow keeps escaping.

What is the difference between an hourglass and a wedge knee pillow?

An hourglass pillow has a dip on both faces, so each knee settles into one. A contoured wedge is shaped to fill the gap between your legs, and some can also go under your knees when you lie on your back. In use they do the same job; pick by listed height first.

Are heart-shaped knee pillows better?

Not better, but bigger. Among the best sellers, heart shapes are among the biggest compact knee pillows, and the tallest fixed-height ones, at 5–7.2″ thick. That suits wide hips or a high towel-test number, and is too much for a narrow gap.

Sources