Sleeping with a Pillow Between Knees: Should You?

Ever wake up with a stiff back, aching hips, or legs that feel oddly misaligned? The solution might be as simple as a pillow between your knees. This small change to your sleep setup isn’t just about comfort—it’s backed by science and used by everyone from chronic pain sufferers to pregnant women and post-surgery patients.

In this guide, discover how placing a pillow between your legs can improve posture, relieve pressure on the spine, and even help with conditions like sciatica, back pain, and hip recovery. It’s a low-effort sleep hack that delivers high-impact results—especially if you’re a side sleeper.

Why Use a Pillow Between the Knees?

Improved Spinal Alignment

When sleeping on the side, placing a pillow between the knees helps keep the hips, pelvis, and spine aligned. Without that support, the top leg tends to pull the spine out of alignment, leading to morning stiffness or persistent discomfort.

This misalignment might not be noticeable overnight, but the cumulative strain it places on the lumbar spine can contribute to issues like herniated discs, nerve impingement, or general lower back tightness. Using a pillow between the legs counteracts that tendency and promotes a more neutral, restful position.

Back Pain Relief

For those living with chronic back pain, particularly lower back pain, even small changes in posture can yield significant relief. The use of a pillow between the legs for back pain is supported by many physiotherapists and chiropractors, especially for side sleepers.

A study published in Work: A Journal of Prevention, Assessment & Rehabilitation found that sleep posture influences back pain in older adults, suggesting side sleeping with proper support may help reduce discomfort.

Sciatica Support

Sciatica occurs when the sciatic nerve is irritated or compressed, typically causing pain that radiates from the lower back down the leg. Sleeping in poor alignment can exacerbate this compression, especially if one leg is crossing over the other or twisting the spine.

A pillow between the knees helps prevent this by maintaining symmetry through the pelvis and spine. For sciatica sufferers, it can be the difference between a restless night and a deep, pain-free sleep.

Pregnancy Comfort

Pregnancy brings with it dramatic shifts in weight distribution and posture. From the second trimester onward, side-sleeping is typically recommended to optimise blood flow and support the uterus. A pillow between the legs offers pelvic stability, reduces strain on the lower back, and improves comfort.

According to guidance from Tommy’s—a UK pregnancy health charity—placing a pillow between the knees is one of the most effective ways to reduce back strain and maintain spinal alignment during sleep.

Post-Surgery Recovery (e.g., Hip Replacement)

Following procedures like hip replacement, sleeping posture becomes critical. Placing a pillow between the legs can help prevent dislocation and ensure healing tissues are not unduly stressed.

This positioning is often recommended in post-operative guidelines from orthopaedic hospitals in the UK and abroad. It promotes both comfort and safety during a critical recovery period.

The Science Behind Sleep Posture and Spinal Health

Sleep is the body's primary recovery mode but poor posture can turn it into a source of stress rather than relief. The spine has a natural curve, and the goal of sleep positioning is to maintain that curvature as closely as possible.

When one leg is unsupported, especially in a side-sleeping position, the pelvis tilts and the spine follows, increasing torsional stress. Over time, this can contribute to chronic pain and muscular imbalances.

How to Use a Knee Pillow Properly

• For Side Sleepers: Position a pillow between the knees so both legs are evenly supported. The knees should be slightly bent with the hips stacked directly on top of each other.

• For Back Sleepers: A pillow under the knees (rather than between) helps support the natural curve of the lower back and can reduce spinal strain.

• Avoid Overly Thick Pillows: A pillow that’s too large or too firm can elevate the leg too much, leading to new misalignments.

Choosing the Best Pillow for Between Knees

When selecting the best pillow between knees, keep the following features in mind:

• Material: Memory foam offers superior support and adapts to individual body shapes.

• Shape: Ergonomically contoured pillows are designed to stay in place and provide consistent support.

• Size: Long enough to support from thigh to knee is ideal for full leg alignment.

• Cover: A breathable, machine-washable cover improves hygiene and temperature control.

For UK shoppers, several trusted brands offer knee pillows tailored to different needs—some are available via the NHS or recommended by osteopaths.

Alternatives to Traditional Knee Pillows

• Full Body Pillows: These provide comprehensive support for the torso and legs.

• Pregnancy Pillows: Specifically shaped for optimal pelvic and spinal alignment.

• Rolled Towels or Cushions: A budget-friendly solution that can still offer some benefit.

Common Conditions That Benefit from a Pillow Between the Legs

• Lower back pain

• Herniated or bulging discs

• Sciatica

• Hip bursitis or hip arthritis

• Knee pain

• Pelvic instability during pregnancy

• Recovery from orthopaedic surgery

Expert Opinions

According to osteopath Phyllis Woodfine, sleeping with pillows between your legs can help with lower back pain.

“It keeps your pelvis in alignment and prevents your back from twisting, keeping it in a neutral position and helping to relieve the tissues and reduce paint. Having your knees on top of one another will also help to prevent your hips and spine from moving into a non-neutral position and prevent twisting, keeping the hips in alignment."

Conclusion

Sleeping with a pillow between the knees offers genuine benefits for posture, spinal alignment, pain relief, and overall comfort. Whether you're pregnant, recovering from surgery, or simply trying to wake up without back pain, this simple adjustment can be game-changing.

A small investment in a well-designed knee pillow—or even just adjusting your sleeping habits—could yield lasting improvements in sleep quality and musculoskeletal health.

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Frequently Asked Questions

Is a pillow between the knees good for back pain?

Yes. It helps maintain the spine's natural curvature and reduces stress on the lower back.

Can I use a regular pillow between my legs?

You can, but contoured knee pillows are better suited to stay in place and provide even support.

Why do pregnant people sleep with a pillow between their legs?

It improves sleep comfort, supports the growing bump, and maintains pelvic alignment.

Does a pillow between knees help with hip pain?

Yes, particularly in side sleepers. It helps reduce strain and stabilise the hip joint.

What is the best pillow between knees for side sleepers?

Memory foam pillows with a contoured shape typically offer the best combination of comfort and support.

How do I stop a knee pillow from slipping during sleep?

Look for pillows with leg straps, or consider a full-body option that supports both legs and the torso.

Is this recommended after hip replacement surgery?

Yes, and in many cases, it’s required to ensure joint protection during early healing.

How thick should a knee pillow be?

Generally 4–6 inches thick—enough to maintain alignment without over-elevating the top leg.