Part of Total knee replacement rehab
How to sleep after a knee replacement: positions, pillows and the bed
Warning signs, and when to get help
How should you sleep after a knee replacement?
In whichever position lets you sleep, with one exception that matters more than the position does.
The NHS is unusually relaxed about this. Its advice on recovering from a knee replacement says you do not need to sleep in a special position after the operation, and in the same breath it gives the one instruction it is specific about: do not sleep with a pillow under your knee. There is no approved posture to hold and no side you are confined to. There is a thing to keep out from behind the knee.
One line outranks the rest of this page. If your surgeon, your physical therapist or your physio gave you an instruction about how to rest the leg, or you came out of surgery with a brace, a splint or a particular set-up, theirs is the instruction to follow. That also covers the smaller group whose operation was not a standard first knee replacement, since a partial replacement, a revision or a replacement done after a fracture can come with a plan that is quite different, and your team is the only source for yours.
The set-up most people arrive at in the first few weeks is lying on your back with the operated leg out straight and a pillow or a folded blanket under the calf and heel. That does two jobs at once. The knee is left straight, and the leg is raised, which is what the NHS asks for to keep the swelling down. The support sits below the knee and under the heel. Nothing goes directly behind the knee.
From about 28 weeks of pregnancy the NHS advises going to sleep on your side rather than on your back, because it says sleeping on your back after that point can double the risk of stillbirth. So use the side-lying set-up described below, and leave lying on your back until after the birth. The NHS also says not to worry if you wake up on your back: settle onto your side again and carry on. Its side-lying tips include a pillow between your legs, which also keeps the operated knee from twisting across the other one, so pick one thin enough that the knee is not propped in a bend all night and keep the straightening work going by day.
Now the part the position pages tend to skip. Gateshead Health's physiotherapy advice after knee replacement puts it plainly: more discomfort at night and trouble sleeping are very common after this operation. A position is not going to fix that on its own in the first fortnight, and if you are reading this at two in the morning having tried everything, you are not doing it wrong. Why a new knee hurts more at night than it does in the afternoon is a different question from which position to lie in, and pain at night after a knee replacement is the page that takes it on. Beyond that, your physical therapist or physio and your surgical team can look at how your day is loaded and at the timing of your pain relief with you.
Why not a pillow under your knee, when it feels better?
The knee settles into the shape it is held in, and a pillow under the knee holds it bent.
The NHS instruction is short and does not explain itself. Gateshead Health's physiotherapy advice supplies the reason: resting the knee on a pillow in a half-bent position feels comfortable and it can go on to affect both how the knee moves and how you walk. The same advice asks for the opposite set-up when you are resting, with the heel on a pillow or a stool so the knee is left to straighten.
The tissue this is about sits at the back of the knee, the capsule and the hamstrings, and it takes up the length it spends most of its hours at. If your knee is one of the ones that will not go fully straight yet, where the support sits stops being a matter of preference. Gateshead Health's advice for a knee that is struggling to straighten is to leave it hanging straight under its own weight (passive extension) while you are sitting, heel on a pillow or a stool, the back of the knee unsupported, for as long as you can tolerate. A reader in that position has the most to lose from a pillow behind the knee overnight, and a knee that is not gaining any more straightening is a thing to raise with your surgical team or physio rather than something to work around with cushions.
Look at the arithmetic of the day and it stops being a close call. The straightening holds in the knee replacement program are measured in minutes, several times a day. A night is seven or eight hours. Whatever the knee is held in for the night is the position with the most hours behind it. One night does not ruin anything. The night quietly outvotes the exercises, every night, and that is what makes this a bigger deal than it looks.
It is comfortable for the same reason it is a problem. A slightly bent knee is the position of least tension, so the leg asks for it, and the pillow is usually put there by someone being kind. This is the single most common thing we take away from people in the first weeks after this operation, and the afternoon version counts too: a footstool that catches you behind the knee does the same job as the pillow, for just as many hours.
The two exercises that pull the other way are the seated heel prop and the knee extension stretch, and both work on the same geometry as the night set-up. Heel supported, knee unsupported, thigh let go so the leg sags under its own weight. If you want one thing to be deliberate about, it is that the support under your leg stops short of the back of the knee, day and night.
A knee that stops gaining movement from one week to the next is worth raising early rather than waiting for the next routine appointment. The reason, and the source for it, are in the warning signs at the end of this page, and a stiff knee and how to improve the bend sets out what counts as a range that has stalled.
Can you sleep on your side after a knee replacement?
Usually yes, once it is comfortable enough to do. Comfort and your own team's instruction are what decide it, not a rule about the joint.
On the position itself the sources are clear enough. OrthoInfo's page on activities after a total knee replacement lists the safe sleeping positions as your back, either side, or your stomach, with no restriction attached and no week attached either. It gives that advice in the section on resuming normal activities once you are home, so it is not a permission that arrives later.
It is the timing where the sources run out. We could not find an NHS page, a NICE guideline or an orthopedic society page that puts a week number on side sleeping after a knee replacement. The figures you will see quoted on other sites are not attributed to anything we could check. So this page gives no week count, and if you want a date for your knee it has to come from your surgical team, who know what was done and how the wound is healing.
Early on, what gets in the way is more ordinary than a restriction. Lying on the operated side puts your body weight onto a fresh wound and a swollen knee, and most people cannot tolerate that for a while. There is also a reason beyond comfort for keeping off it early. OrthoInfo asks you to keep the wound area clean and dry, to change the dressing only as your surgeon directs, and to tell your doctor immediately if the wound looks red or begins to drain, so while the dressing is on or the wound is not yet dry and closed, keep your body weight off the front and the side of the knee. A wound that starts leaking again, or that is still leaking in the second week, is on the warning list at the end of this page.
Lying on the other side is far more comfortable and is where most people end up once they can turn at all, often with the operated leg resting on top of the other one. Resting one leg on the other while you are lying down is a different thing from the NHS instruction not to sit with your legs crossed for the first 6 weeks, which is about sitting. Keep the legs stacked rather than twisted across each other, because twisting the knee is what the NHS asks you to avoid as much as you can while you are recovering.
That second position has one cost worth knowing about, and it is the same cost as the pillow. The top knee tends to settle bent, and it stays there for hours. It is not a reason to lie awake on your back instead. It is a reason to be honest with yourself about the straightening work in the day, because on a night spent curled up, that work is the only thing holding the other end of the rope. The exercises for the first 2 weeks set out how that work is spread through a day.
If you have had a hip replaced as well, do not carry the sleeping advice across between the two joints. A hip has restrictions on how far it may bend and turn, and a knee has the opposite aim, which is getting the bend back and keeping the straightening. Sleeping positions after a hip replacement is a separate page for a reason.
Can you sleep on your front after a knee replacement?
Not for the joint itself, and in one respect it is the friendliest position there is.
Lying on your front leaves the knee straight without you arranging anything, which is the direction the whole rehabilitation is heading in, and OrthoInfo names your stomach among the positions it calls safe after this operation. What stops people is everything around the joint rather than the implant: the wound and the dressing, pressure across the front of the knee and the kneecap, and finding somewhere comfortable for the foot and ankle at the end of a straight leg. The wound point from the section above applies most obviously here, because lying face down presses the dressing and the incision into the mattress, so leave front sleeping until the wound is dry and closed.
No source we could verify gives a week or a month figure for when front sleeping becomes possible after a knee replacement, and the month figures that circulate for it carry no attribution. We do not repeat them. The practical answer is that you will know: it either hurts at the front of the knee or it does not. Try it when you are curious, come off it if it is sore, and ask your surgical team if anything about your wound or your operation makes you unsure.
Raising the leg for swelling without bending the knee
This is where the two NHS instructions seem to collide, and the whole thing turns on where the support sits.
The NHS asks you to keep the leg raised as much as possible to reduce swelling, and it asks you not to stand for long periods, which brings the swelling into your ankles. It also asks you not to sleep with a pillow under your knee. Both are right, and they are not in conflict, because raising a leg and propping a knee are two different physical arrangements that happen to use the same pillow.
The arrangement that does both jobs is one line of support running from below the knee to under the heel, with the knee itself left floating. Gateshead Health describes elevating the leg on a stool or on the bed for the swelling, with the heel resting on the pillow or the stool so the knee is left to straighten. If you can slide a hand into a gap behind your knee, the set-up is right. If the pillow is pressing into the back of the knee, slide it down toward the ankle.
One part of that set-up belongs to the night rather than the afternoon, and it is rarely mentioned anywhere. A heel resting on the same spot for eight hours is carrying the weight of the leg on one small bony point. The NHS names the heels first among the places pressure ulcers form, and lists recent surgery, difficulty moving, fragile skin, poor circulation and problems feeling sensation among the things that make one more likely, which between them describe a good many people in the first weeks after this operation. So let the support run along the calf rather than under the heel alone, use something soft instead of the hard edge of a stool, move the leg when you wake, and look at the skin on your heel once a day. If you find a patch that is discolored and does not change color when you press it, or skin that feels warm, spongy or hard, see your doctor rather than waiting for it to break open, and get urgent advice the same day if that skin becomes hot, swollen or red, leaks pus, or comes with a temperature.
Two things belong to the night and not to the day. A long still spell is one half of what raises clot risk after this operation, which is why the warning signs below name a spell of being much less mobile than usual as part of the picture. Ankle pumps are the thing to do while you are lying there, and they cost nothing. Then the compression stockings, if you were sent home in them: the NHS asks for compression stockings to be worn at all times, taken off only for washing, and says most people need them for at least 6 weeks, which answers the question most people ask about the night. The rest of the swelling, ice and clot routine sits on the main knee replacement page and is not repeated here, and how long swelling lasts after a knee replacement is the page for how long the swelling itself goes on.
If you are more than about 28 weeks pregnant, use the side position described above rather than the back one.
Getting in and out of bed, and turning over in the night
No national guideline describes a method for this, so what follows is what physical therapists and physios teach at the bedside. If your team showed you a version of it, use theirs.
Getting in, the thing that makes it work is sitting far enough up the bed before you start lying down, nearer the pillow than you think, so you are not then shuffling upward on your back with a sore leg. Sit on the edge, lower yourself onto your forearm and elbow, and bring the operated leg round as you go down rather than afterward. The operated leg does not have to lift itself. Use a hand under the thigh, or hook the other foot under the ankle and let the good leg do the work.
One thing not to do on the way onto a bed, especially a high one: do not kneel on the new knee to climb on. The NHS says not to kneel on the new knee until your doctor says you can, and getting onto a bed is one of the places people do it without thinking. Sit and shuffle instead, and kneeling after a knee replacement covers when that changes.
Getting out is the same sequence backward. Swing the legs out as a pair, push up through your hands and the other leg, and sit on the edge for a moment before you stand. That pause is not just about the knee. Standing up quickly in the night is when people get the lightheaded spell that is in the warning signs below, and a fall onto a new knee is a serious event in its own right: OrthoInfo warns that a fall in the first few weeks after surgery can damage the new knee and may lead to further surgery.
Turning over is a matter of moving the leg as one piece. Bend the other knee, push through that foot, and take the operated leg with you, with a hand under the thigh if it will not come. What you are avoiding is the knee twisting while the foot stays put, and the NHS asks you to avoid twisting your knee as much as possible while you are recovering.
Make the route to the bathroom boring before you need it. Crutches or your stick where your hand lands rather than across the room, a light you can reach without standing up, and nothing on the floor between the bed and the door. OrthoInfo's advice for anyone on a walking aid asks for well-lit rooms and a nightlight along the route between the bedroom and the bathroom. Put the phone where your hand lands too, not across the room on a charger, because the fall you would need help after is the one that leaves you on the floor away from it. If you live alone, that single decision is worth more than everything else in this section.
If both knees were replaced, there is no good leg to do the work in any of the methods above, so none of them transfers as written. Use your hands under each thigh, start from sitting higher up the bed rather than flat, and have your physio, physical therapist or occupational therapist watch you get in and out before you go home rather than working it out in the dark on the first night. A bed on the ground floor is worth arranging for the same reason. Decisions about where the bed goes and what you need around it are better made before the operation, and they are covered in what to pack and prepare at home.
What if you wake up curled up, or with a pillow under your knee?
Nothing has been undone. One night in an awkward position does not damage a knee replacement, and waking up somewhere you did not start is normal.
Straighten the leg out, give it a few minutes supported under the heel, and get on with the day. In clinic the first ten minutes after you get up are the stiffest of the day for most people, and that is why the early work is front loaded: quad sets to wake the thigh up and heel slides to get the bend moving are both reasonable to do before you are properly out of bed.
Waking up curled every single night is a different signal, and it is usually about the set-up rather than about you. Something is inviting the bend: a pillow that has migrated under the knee, a mound of pillows that leaves the knee as the high point, or a side-lying position with nothing supporting the top leg. Rebuild the arrangement so the straight option is the easy one, and treat the daytime straightening holds as the part you can actually control.
The nights when nothing helps
Some weeks after this operation, no position is comfortable. Gateshead Health names it as very common, and saying so is more useful than another list of positions.
What a physiotherapy page can honestly offer you is the daytime half of the problem. Exercises spread across the day rather than done in one morning block. The leg raised through the day instead of hanging down in a chair for ten hours. Walking that goes up gradually rather than in one long trip that shows up at bedtime. None of that is a cure for a bad night, and all of it changes what the knee is like by the evening.
What a physiotherapy page should not offer you is anything about sleep medicines, supplements or alcohol, or how to time your pain relief. Those belong to your prescriber, your pharmacist or your surgical team. Never stop or change a prescribed medicine on your own.
If the nights are not improving at all, use the route the system is supposed to have given you. NICE recommends that people doing their own rehabilitation after a joint replacement are given clear goals and a point of contact for advice and support, and that supervised outpatient rehabilitation is offered to people who are having difficulty with daily activities, who have ongoing functional problems with specific needs, or who are not meeting their goals on their own. Weeks of broken sleep that are stalling your exercises fit that description, and the point of contact exists to be used rather than saved.
When a bad night needs checking
Most bad nights after a knee replacement are the operation settling down. A few are something else, and the list below is about telling them apart quickly rather than about sleep.
Wake up short of breath, with chest pain, or with pain in your upper back that is worse when you breathe in, and that is an emergency call, whatever your leg looks like. Lying still for long stretches is one half of what makes a clot more likely after this operation, so a calf or thigh that is newly swollen, warm, tender or sore to touch needs advice the same day, as does a leg that is swelling further day by day instead of settling.
Get advice the same day as well for a wound that is more red, hot or painful, or that starts leaking again, for a knee whose pain keeps building both when you move it and when you rest it, and for tiredness and breathlessness that are mounting rather than easing. Lightheadedness when you stand up at night that does not pass in a minute or two belongs in the same group.
Contact your physio or surgical team within a few days if the knee has stopped bending or straightening any further from one week to the next, or if it feels unstable. Each of these has its own line below, with its own urgency, and the stiffness line explains why the date you raise it matters.
Two more are on the list below for the same reason, and neither is about sleep. If you cannot straighten the knee or lift the leg out straight when you could the day before, or you can feel a dip just above or just below the kneecap, that is a same-day call: the tendon at the front of the knee can tear, and it does not take a fall to do it. And months or years on, pain in the knee that had settled and has come back, or pain that is worse month by month, is worth a review rather than another change of pillow. A knee that becomes hot, red or swollen at any time after the operation, even years later, is a same day call on its own, with or without pain and with or without a temperature. A normal temperature is not an all clear either: OrthoInfo's page on infection after a joint replacement says fever is no longer considered a sign of an infection after a joint replacement, and that the signs can be as little as mild redness and swelling.
Related exercise programs
Warning signs
Get emergency help now
- Emergency: since your operation, you suddenly become short of breath, you get chest pain or pain in your upper back that may be worse when you breathe in, you cough up blood, your heart is beating very fast, or you faint. Call emergency services straight away, even if your leg looks normal. These can be signs of a blood clot in the lungs (pulmonary embolism).
- Emergency: after a fall or a knock, you cannot put weight on the leg, your knee or thigh is very painful, or the leg looks out of shape or shorter than the other. Go to an emergency department straight away, and do not drive yourself. If you cannot get up, call emergency services. A broken bone around a knee replacement is rare, but it needs treatment in hospital. If a smaller fall or knock leaves the knee newly painful, swollen or bruised, even if you can still walk on it and the leg looks normal, stop the exercises, go back to your crutches or sticks and keep your full weight off that leg, and get it checked by your surgical team the same day. A break in the bone around a new knee is not always obvious at first, and walking normally on one can move the broken ends apart.
Get help today
- Same day: a calf or thigh that is newly swollen or getting more swollen, warm, tender, red or darker than usual, has swollen veins that are sore to touch, or has a throbbing or cramping pain that does not fit your injury or condition, or that feels different from normal muscle soreness after exercise. This can be a sign of a blood clot (deep vein thrombosis), especially after surgery, an injury, time in a cast or boot, a long trip or a spell of being much less mobile than usual. Get medical advice the same day. If you are also short of breath or have chest pain, call emergency services.
- Same day: swelling in the operated leg that is increasing from day to day instead of settling, including swelling spreading into your calf, ankle or foot, pain in your leg or calf away from the wound, increasing pain in your calf, or tenderness or redness above or below your knee. Get medical advice the same day. Swelling is expected after this operation, and it can be moderate to severe in the first days or weeks, but OrthoInfo asks you to tell your doctor about new or severe swelling because it can be the warning sign of a blood clot, and increasing swelling of the calf, ankle and foot, increasing calf pain, and tenderness or redness above or below the knee are all on its list of clot signs. Your clot risk does not end on the day your tablets or injections do. If you are also short of breath or have chest pain, call emergency services.
- Same day: you are taking tablets or having injections to lower your risk of a blood clot and you notice blood in your urine, black or bloody stools, bleeding gums, a nosebleed that goes on and on, bruising far beyond what the knock would explain, or you are being sick or coughing up blood. Get medical advice the same day, and do not stop the medicine on your own. Bleeding more easily is the known trade-off of these medicines (NHS), and the dose or the type may need looking at. Go to an emergency department if the bleeding will not stop, you feel faint, or you bang your head while you are taking it, even if you feel fine, because the NHS advises getting urgent advice after a head injury on medicine that thins your blood and only a hospital can scan for a bleed inside the head.
- Same day: your wound becomes more red, hot, swollen or painful, starts to leak or ooze, is still leaking in the second week or has never stopped, has pus coming out of it or its edges start to come apart, or you have a high temperature or feel hot, cold or shivery. Contact your surgical team or get medical advice the same day. Redness can be harder to see on brown or black skin. If you feel very unwell, go to an emergency department. If you have a very high or very low temperature, shivering you cannot control, you are breathing very fast or finding it hard to breathe, you are confused or your speech is slurred, your skin, lips or tongue look blue, gray, pale or blotchy (on brown or black skin this can be easier to see on the palms of the hands or soles of the feet), or you have a rash that does not fade when you press it, call emergency services, as this can be sepsis.
- Same day: in the days or weeks after your operation you are getting more and more tired, breathless doing everyday things such as walking to the toilet or getting dressed, dizzy or lightheaded, your heart is racing, or your skin looks paler than usual. Contact your surgical team or get medical advice the same day. Tiredness and breathlessness that build up like this are not part of the usual recovery. Blood loss during and after a knee replacement can leave you short of red blood cells (anemia), which is treatable, and a slow bleed or an infection can show up the same way. If breathlessness comes on suddenly, or you get chest pain, call emergency services, as the emergency line above explains.
- Same day: since your operation, the redness, warmth, swelling or pain in your knee is not getting better or is getting worse, for example the knee pain keeps building both when you move and when you rest. Contact your surgical team or get medical advice the same day, as this can be a sign of infection around the new joint. If you feel very unwell, go to an emergency department.
- Same day: at any time after your operation, even years later, new pain in your new knee along with a high temperature or feeling hot, cold or shivery, or a knee that becomes hot, red or swollen, which counts on its own, with or without pain and with or without a temperature. Contact your surgical team or get medical advice the same day. A new joint can become infected long after the operation, and that needs treating quickly. A normal temperature is not an all clear: OrthoInfo says fever is no longer considered a sign of an infection after a joint replacement, that the signs can be as little as mild redness and swelling and sometimes there are none at all, and that increased pain or stiffness in a joint that had been working well is one of them. So do not wait for a temperature before you report new or increasing pain in your new knee to your surgical team.
- Same day: you suddenly cannot straighten your knee or lift your leg straight when you could before, often after a pop, a tearing feeling or a stumble, or you notice a dip just above or below your kneecap, or you suddenly cannot put weight on the leg, even without a fall. Keep your weight off it and contact your surgical team the same day. If you cannot reach them that day, go to an emergency department. A tendon at the front of the knee may have torn, and a repair works better when it is done soon.
- Same day: a leg or foot that is getting weaker, for example your foot drags, catches on the ground or slaps down when you walk (foot drop). Get medical advice the same day. Until it has been checked, use your walking aid, hold a rail on stairs and keep off uneven ground, because a foot that catches trips you and a fall onto a new knee can damage it. If the weakness is getting worse by the hour, go to an emergency department.
- Same day: new numbness, tingling or burning in your lower leg or foot, beyond the numb patch of skin around your scar. Contact your surgical team or get medical advice the same day. If it started after a fall or an injury, or your foot or toes turn cold, pale, blue or gray, call emergency services or go to an emergency department straight away, and do not drive yourself.
- Same day: dizziness, lightheadedness, blurred vision or feeling faint when you stand up that is new for you, does not pass within a minute or two, keeps happening, or has made you fall. Sit or lie down, and get medical advice the same day. This can be a drop in blood pressure on standing (postural hypotension), a type of low blood pressure, which the NHS lists among the causes of falls, and your doctor can check it. Tell them about your medicines, because some can cause it. If it does not settle within a few minutes of sitting or lying still, call emergency services. If you faint, call emergency services, even if you come round quickly, because the NHS says to call them when someone faints while exercising or is badly hurt, and a fall onto a new knee can damage it.
- Same day: dizziness or feeling faint during or after exercise, other than the brief lightheadedness as you stand up covered in the line above, without any of the emergency signs above. Stop the exercises and get medical advice the same day. If you faint, it does not settle within a few minutes of sitting still, or you cannot stand or walk steadily, call emergency services.
Book an appointment
- Within a few days: your knee is not bending or straightening any further from week to week, is getting stiffer, or feels unstable or gives way when you stand or walk. This is not an emergency, but contact your physio or surgical team within the next few days rather than waiting for your next routine appointment, and keep using your walking aid until they have checked it. A stiff knee is easier to free up early than late: where it has to be freed up under anesthetic, doing that earlier, generally within about 6 to 12 weeks of the operation, is associated with regaining more movement than doing it later, although how much any one knee gains also depends on how stiff it was to begin with, on who is suitable and on the rehabilitation afterward. So the date you raise it matters (Hosanee and colleagues, 2026). If the knee has given way and let you fall, or it gives way on stairs, hold a rail and use your walking aid every time, and stay off stairs on your own until you have been seen.
- Within a few days: you have had a fall, even if you were not hurt, or you keep tripping, stumbling or feeling that your legs might give way. Book an appointment with your doctor within a few days and ask about a falls assessment. Tell them about every fall, even the ones where you were not hurt.
- Routine: pain in your new knee that had settled and has come back, or pain that is getting worse month by month, for example pain that starts as soon as you stand up and begin to walk. This is not an emergency, but ask your surgical team for a review, as the parts of a new joint can loosen or wear over the years. Get medical advice the same day instead, not a routine appointment, if the knee also becomes hot, red or swollen, or you have a high temperature or feel hot, cold or shivery, or the pain is building week by week rather than month by month. A new joint can become infected years after the operation, and the two can feel similar at first.
Common questions
How should you sleep after a knee replacement?
The NHS says you do not need to sleep in a special position after this operation, and the single thing it asks is that you do not sleep with a pillow under your knee. Most people in the first few weeks end up on their back with the operated leg out straight and a pillow under the calf and heel, which also keeps the leg raised for the swelling the way the NHS advises. The support belongs below the knee and under the heel, not behind the knee. From about 28 weeks of pregnancy the NHS advises going to sleep on your side rather than on your back, because it says sleeping on your back after that point can double the risk of stillbirth. So use the side-lying set-up instead, and leave lying on your back until after the birth. The NHS also says not to worry if you wake up on your back: settle onto your side again and carry on. Whatever your own surgical team told you about resting the leg comes first.
Can I sleep on my side after a knee replacement?
Usually yes, once it is comfortable enough to do, and the limit is comfort and your own team's instruction rather than a rule about the new joint. OrthoInfo says you can safely sleep on your back, on either side, or on your stomach after this operation. What nobody publishes is a week number: we could not find an NHS page, a NICE guideline or an orthopedic society page that puts one on side sleeping after a knee replacement, so any figure you see quoted for it has no source behind it and we do not repeat one. Lying on the operated side puts your body weight onto a fresh wound and a swollen knee, which is what stops most people early on, and OrthoInfo's instruction to keep the wound clean and dry is a reason to keep off it until the wound is dry and closed. Lying on the other side is more comfortable, and the thing to watch there is that the operated knee tends to rest bent for hours, so keep the straightening work going by day. Ask your surgical team whether anything about your knee changes this.
Should I put a pillow under my knee at night?
No. The NHS advises against sleeping with a pillow under your knee, and Gateshead Health's physiotherapy advice after knee replacement says the same thing about resting the knee on a pillow in a half-bent position: it feels comfortable and it can go on to affect how the knee moves and how you walk. A knee held in a small bend for seven or eight hours is being trained in the opposite direction to every straightening exercise you do in the day, and the night is far longer than the exercises. The same goes for a footstool that catches you behind the knee in the afternoon. If you are raising the leg, put the pillow under your calf and heel so the knee is left straight.
Can I sleep on my front after a knee replacement?
Front lying is the one position that leaves the knee straight without you having to arrange anything, which is the direction this rehabilitation is going in, so it is not a problem for the new joint itself. OrthoInfo includes sleeping on your stomach among the positions it calls safe after this operation. What stops people is the wound, pressure across the front of the knee and the kneecap, and getting the foot comfortable. Lying face down presses the dressing and the incision into the mattress, and OrthoInfo asks you to keep the wound clean and dry, so leave front sleeping until the wound is dry and closed. No source we could verify gives a week or month figure for when front sleeping becomes possible after a knee replacement, and the month figures that circulate for it are not attributed to anything, so this page does not repeat them. Try it when it is comfortable, stop if it is not, and ask your surgical team if you are unsure.
Do I have to keep my leg straight all night?
You do not have to hold it straight, and you cannot control what you do while you are asleep anyway. What you can control is the set-up you get into: nothing propping the back of the knee, and the support under the calf and heel if you are raising the leg. Waking up curled up for one night does not undo the operation. Waking up curled up every night usually means the pillows are arranged in a way that invites it, which is worth changing, and it is a reason to be more deliberate about the straightening holds during the day.
How do I turn over in bed after a knee replacement?
Move the leg as one piece rather than letting the knee twist. Bend your other knee, push through that foot, and take the operated leg round with you, using your hands under the thigh if it will not come. The NHS asks you to avoid twisting your knee as much as possible while you are recovering, and a slow deliberate roll is how you keep to that. No published guideline describes a turning method, so this is what physical therapists and physios teach at the bedside, and your own team's version comes first if they showed you one.
References
- NHS. Recovering from a knee replacement. Page last reviewed 9 September 2026. https://www.nhs.uk/tests-and-treatments/knee-replacement/recovery/
- American Academy of Orthopaedic Surgeons. Total knee replacement. OrthoInfo. https://www.orthoinfo.org/en/treatment/total-knee-replacement/
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Written and checked by the PocketPhysio editorial team. Last updated 2026-10-17.
This page is general education, not a diagnosis or a personal treatment plan. See a physiotherapist or doctor for advice about your own situation.