In simple terms, an irritated hip struggles with three specific things. Understanding them is the key to understanding why your sleep position matters so much.

The first is adduction. That’s when your leg crosses in towards the middle of your body — think of your knees dropping together. The second is internal rotation, which is when the leg rolls inward, again with the knees falling towards each other. The third is end range flexion, which is the hip being bent up too far towards your chest.

On their own, each of these movements will aggravate a hip that’s already sensitive. They compress and close the joint in exactly the way it doesn’t want. And here’s where sleep becomes a problem: when you lie on your side, your hip naturally wants to drop into all three of these positions at once. The top leg falls inward, crosses over, and the whole hip sinks into the position it hates most — and you hold it there for hours while you sleep.

That’s the part most people never realise. You’re not doing anything obviously wrong. You’re simply lying down to rest, and gravity is quietly pulling your hip into a position it can’t tolerate, all night long. No wonder you wake up feeling worse.

Most people with hip pain do one thing instinctively, and it’s actually the right instinct: they avoid lying on the painful hip. If your left hip hurts, you roll onto your right side to keep the weight off it. So far, so sensible.

The problem is what happens next. Without any support, that top leg — the painful one — simply drops forward and down. It falls straight into adduction and internal rotation, closing the joint exactly as we described above. So you’ve taken the pressure off by not lying on the bad hip, but you’ve created a new problem by letting it collapse inward instead.

This is why so many people go to bed on their good side, convinced they’re doing the right thing, and still wake up with the hip feeling worse than when they got in. They’ve solved one half of the equation and accidentally created the other. It’s a frustrating cycle, and it keeps a lot of people stuck — they assume the pain is just getting worse on its own, when really it’s the eight hours of poor positioning every single night that’s holding back their recovery.

If that sounds familiar, the fix below will likely make an immediate difference.

Here’s the answer, and it really is this simple: a pillow between your knees.

Lie on your good side, and place a pillow between your knees and thighs. The crucial detail is that it shouldn’t sit only at the knees — you want it running up the full length of the thigh so the whole leg is properly supported. When you do this, the pillow keeps your top leg level. It stops the leg dropping into adduction and internal rotation, which means you’re holding the hip in a neutral, comfortable position instead of letting it sink into the positions it can’t stand.

For a lot of people, the difference is significant and often instant — many notice it on the very first night. You’re essentially removing the thing that’s been aggravating the hip for hours on end, and giving the joint a chance to rest in a position it’s actually happy with.

There are a couple of things to get right, though, because they make all the difference:

• The pillow needs to be thick enough. A thin, flat pillow won’t cut it — your leg will simply squash it down and keep dropping anyway. You want a firm, reasonably chunky pillow, or better still a dedicated knee pillow designed for exactly this job. The whole point is to stop the leg falling, so it has to be substantial enough to actually hold it level.

• Keep the top knee level with the hip. Don’t pull it up too high towards your chest. If you do, you bring in that third problem position — end range flexion — and undo some of the benefit. Roughly level with the hip, or no higher, is the sweet spot.

Get those two details right and you’ve turned the worst sleeping position into the best sleeping position for hip pain, without buying anything more complicated than a decent pillow.

Side sleeping isn’t for everyone, and if it’s not working for you, lying on your back is generally a good option for hip pain. On your back, the hip naturally sits in a fairly neutral position, which means it isn’t being forced into any of the three positions it dislikes.

If you want to take it a step further, place a small pillow under your knees. This takes a little tension off the front of the hip and keeps everything relaxed, which can make back sleeping even more comfortable. The main things to avoid are crossing your legs or letting your feet fall heavily outward for long stretches, as both can gradually pull the hip out of that comfortable neutral position over the course of the night.

Between supported side sleeping and a well-set-up back position, most people can find something that lets them get through the night without aggravating the joint.

So if you’re waking up with hip pain, the very first thing to check is your position. If you’re on your good side, use a pillow between the knees that runs up the full length of the thigh, and keep the top knee level with the hip or no higher. If you prefer your back, a small pillow under the knees does the job. That’s it — a small change, but a genuinely big difference, and one that costs you almost nothing to try tonight.

Give it a go for a few nights and pay attention to how you feel when you wake up. If the pillow trick helps, it’s worth making it a permanent part of your routine while you work on the underlying cause of the pain. And remember that good sleep positioning supports your recovery rather than replacing it — keep up with the other things that are helping your hip, and let a good night’s rest work alongside them.

Joe Sharp
BSc (Hons) Physiotherapy