Part of Total knee replacement rehab
Swelling after a knee replacement: how long it lasts
Warning signs, and when to get help
How long does swelling last after a knee replacement?
Swelling after a knee replacement runs for months, and nobody can give you a date. What can be given is the shape of it. That is more use anyway, because almost everyone who asks is really asking whether the knee in front of them is going the right way.
Three patient-facing sources put figures or descriptions on it. OrthoInfo, the patient information service of the American Academy of Orthopaedic Surgeons, describes moderate to severe swelling in the first few days or weeks after surgery, and then mild to moderate swelling for about 3 to 6 months after surgery. Arthritis UK gives a shorter figure for part of it: swelling particularly affecting the ankle and the foot, which may last up to three months or so, with the ankle swelling usually settling as your walking improves, and swelling of the knee itself also common over the first few months. The South Tees Hospitals leaflet, written for people in the UK after this operation, names swelling down the leg and into the calf, and around the scar, among the things to expect. None of them gives an end date, and none of them is wrong to withhold one. OrthoInfo's 6 months is the longest figure any of the three gives, which matters later on this page.
For the shape, there is a study that actually measured it. Pua followed 85 people who had a total knee replacement on one side, and measured the knee with bioimpedance before surgery and then on days 1, 4, 14 and 90. Swelling rose about 35% above the preoperative level by day 1, then came down, and was still about 11% above it on day 90 (Pua, 2015). That is the curve, not a target: a steep peak in the first day or two, a fast fall over the first weeks, then a long, flat, boring tail. Those percentages were produced with laboratory equipment in a research setting, and they are not something to measure or estimate at home.
That tail is why the numbers you find online disagree so violently. One page says one to two weeks, another says six months, another says a year, and each one is describing a different part of the same curve without saying which. The fast fall is over in weeks. The knee looking like the other knee takes much longer.
What this page covers, and what it does not. It is written about a knee after a first total replacement, where nothing else is being investigated as the cause. A second operation on a knee that has already been replaced, a knee replaced as part of treating a broken bone, or swelling that your team is already looking into for another reason are outside it. And your surgical team's version always comes first: they know which operation you had, what they found while they were in there and what else is going on with you, and if their account and this page disagree, theirs is the one to act on. The whole recovery arc, with every figure attributed, is on the knee replacement recovery timeline.
Is this much swelling normal, and why is the whole leg swollen?
Almost always, yes. Usually the part that alarms people most is the part that was most expected. People come in braced for a swollen knee and are not braced for a swollen shin, a thick ankle, a puffy foot and bruising that has tracked halfway down the calf. South Tees lists swelling down the leg and into the calf among what follows this operation, so a leg that looks like that is doing what the leaflet describes.
Two different things are swollen at the same time, and they behave differently. There is fluid inside the joint itself, which clinicians call an effusion, and that is what makes the knee feel tight and full and hard to bend right at the end of the range. And there is fluid in the soft tissue of the leg. That is the part that reaches the shin, the ankle and the foot, and the part that changes most through the day. On a discharge letter or a clinic note you may see swelling written as edema, or as oedema in the UK, Australia and New Zealand. They are the same thing.
Being upright is what drives the leg's share of it, and the sources treat it the same way. The NHS asks you to keep the leg raised as much as possible to reduce swelling, and tells you not to stand for long periods of time as this could cause swelling in your ankles. Those two sentences, read together, are the whole explanation for why the ankle is involved at all.
Three things sit outside all of that, and they are worth knowing here rather than at the bottom of the page. Swelling that is increasing from day to day instead of settling. A knee that goes tight and tense over a few hours rather than over days. And a knee that is hot or red, a wound that is leaking, or a temperature or feeling hot, cold and shivery. Each of those is medical advice the same day, not a reason to rest the leg and look again tomorrow, and the warning signs at the end of this page give the route for each.
Bruising follows the same route and is on its own timetable. It comes out after the operation, not during it, moves downward, and changes color as it clears. It usually looks worst at the end of the first fortnight, just as people start to think they should be getting better. The exercises for weeks 0 to 2 deals with that first fortnight properly, including what is normal in it, so this page will not go over the same ground.
Why is it worse in the evening and after a walk?
Because by the evening the leg has spent the whole day below the level of your heart, and in bed it spends the night level with it. That explains the daily rise and fall, not the swelling itself, and it rests on the two NHS instructions above: raised means less swelling, long periods standing mean more.
This is the most useful line on the page. Morning is the low point of the day and evening is the high point, every day, for months. So an evening knee compared with yesterday morning's knee will tell you nothing except what time it is. If you are going to keep an eye on your own swelling, and it is reasonable to, look at it at the same time of day, and the morning is the better one because it is the measurement that has had the whole night to settle.
On top of the daily rise and fall sits whatever you asked the leg to do. A longer walk, a first trip out, an afternoon on your feet or a harder session all add to the evening, so the biggest evenings follow the biggest days. That pattern is practice experience rather than a published finding, but it is consistent enough that most people spot it themselves within a fortnight.
So a bad evening after a big day is not a setback. And a knee that is swollen in the morning, before the day has had a chance to do anything to it, is worth more of your attention than a knee that is swollen at nine at night.
How to reduce swelling after a knee replacement
Nothing here is dramatic. All of it is dull, which is the main reason it gets dropped. Your physical therapist or physio will set the specifics for your knee, and anything your team has limited takes priority over the general advice below.
Raise the leg, and raise it properly. The NHS asks for the leg to be kept raised as much as possible to reduce swelling, and OrthoInfo asks for the leg to be elevated with ice applied. How high is worth a figure, and Arthritis UK gives one: raising your foot above hip height, on a footstool or similar, is a good way of reducing swelling. Done properly means the whole leg supported from the thigh to the heel, foot higher than the hip, with the knee straight. It does not mean a pillow underneath the knee. The NHS is direct about that one: do not sleep with a pillow under your knee, and it adds that you do not need to sleep in a special position after the operation. The reason is worth knowing, because it stops people doing it by accident on the sofa as well as in bed. A knee left bent for hours is comfortable precisely because it is bent, and hours of that works directly against the straightening you are trying to get back. A rolled towel or a cushion under the calf and ankle, with nothing under the knee, raises the leg and keeps it straight at the same time. The seated heel prop is the same idea turned into an exercise, and how to sleep after a knee replacement covers the same arrangement at night, where the hours add up. One limit on all of this, because an afternoon with the leg up is also an afternoon of sitting still: Arthritis UK asks you to get up and walk around for at least five minutes every hour, to help lower the risk of a blood clot.
Keep the foot and ankle moving. OrthoInfo says foot and ankle movement is encouraged immediately after surgery to increase blood flow in the leg muscles, both to help prevent leg swelling and to keep blood clots from forming. That makes ankle pumps one of the few things on the list that does two jobs at once. Quad sets and heel slides are the other early movement exercises, and the program with its doses sits on total knee replacement rehab.
Move early, without waiting for the swelling to settle. This one catches people out, because a tight, swollen leg feels like a leg that should be rested. NICE, in its guideline on joint replacement, recommends that rehabilitation is offered on the day of surgery where that is possible and within 24 hours otherwise (NICE NG157). Moving is part of the treatment for the swelling, not a risk to be taken with it.
Wear the stockings as they were prescribed. 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. They are there to lower the risk of a blood clot, and OrthoInfo notes that compression stockings may also help reduce swelling. Wear the ones your team gave you, in the way they told you. If a stocking will not go on, rolls down, digs in or leaves marks, tell your team instead of giving up on it.
Ice, with the usual care. Ice goes alongside elevation in both OrthoInfo's advice and the South Tees leaflet, which says ice and elevation are key to controlling the swelling and can help with pain. How to apply it safely, including the care needed over the numb skin around the scar, is set out on total knee replacement rehab and is not repeated here. The research on ice and swelling specifically sits in the next section but one, and it is less impressive than you might assume.
Break up the standing. The NHS warns against standing for long periods, so the fix is the same one every physio gives for every swollen leg: sit down before you have to, and get the leg up while you are sitting.
Using swelling to judge your exercise, and the one time you cannot
Read this part in the order it is written, because the first paragraph outranks the rest of the section.
If the swelling in your leg is increasing from day to day rather than settling, if the knee has gone tight and tense over a few hours rather than over days, if it is spreading into the calf, ankle or foot, if the knee is hot or red, if the pain keeps climbing while you are resting and not only while you move, if the wound is leaking, or if you have a temperature or feel hot, cold or shivery, then the next thing to do is get medical advice the same day. Not adjust your exercises. Not wait and see how tomorrow looks. The warning signs below give the route for each of those.
With that settled, swelling is a genuinely good gauge of whether a session suited your knee, and the way to read it is simple. The morning after is the measurement, not how the knee felt while you were doing the exercises. Plenty of sessions feel fine at the time and show up at seven the next morning. So compare this morning with yesterday morning. A knee that is a bit more swollen and a bit stiffer than it was the morning before, and that settles again within the day, means you were at the edge of what it could take, which is a reasonable place to be some of the time. A knee that is clearly more swollen and sorer, and still is the morning after that, means the session was too big. Drop back a step rather than stopping altogether, and go again. The pain monitoring model is the general version of this way of working, and the exercises for weeks 2 to 6 covers the window where people most often push too hard because progress has flattened.
Now the exception, and it is the reason this page exists in the shape it does. Doing too much and an infection around the new joint produce the same thing: a knee that is more swollen and hurts more. From the inside they do not feel different. OrthoInfo's own list of possible signs of infection around a knee replacement includes increasing redness, tenderness or swelling of the knee wound, and increasing knee pain with both activity and rest. So swelling is not proof that you simply overdid it. 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. The habit worth building is that a more swollen, more painful knee gets checked against those few extra signs before it gets blamed on yesterday's walk, and if any of them is there, the phone comes before the exercise plan.
What does not help, and what we cannot tell you
There is a market in this, and it is worth knowing what the evidence actually supports before you spend anything.
The continuous cooling machines are the clearest example. A 2024 systematic review and meta-analysis of cryotherapy after knee replacement found that a continuous cold flow device gave knee swelling comparable to plain cold packs, and the authors still recommended traditional cold packs (Liang and colleagues, 2024). A separate review of seven trials covering 519 people likewise found no difference in knee swelling between continuous and traditional cold treatment, and came to the same recommendation on grounds of cost (Liu and colleagues, 2023). So the expensive version of ice is not the better version of ice.
Ice itself is less proven than its reputation, at least for swelling. A systematic review of randomized trials on cryotherapy for swelling after knee replacement found that in six of the eight trials the effects were not significantly different, and that the methods varied enormously, from short ice pack sessions to automated devices run for up to 48 hours (Lee and colleagues, 2023). That is not a reason to throw your ice pack away, because the sources above still pair ice with elevation and because the same 2024 review that found no advantage in the machines did find cold treatment lowered pain scores in the first three days after the operation compared with no cold treatment, and recommended its routine use (Liang and colleagues, 2024). Pain relief is what lets you move. It is a reason not to expect ice to be the thing that fixes the swelling, and not to feel you are failing if it is not.
One honest gap, worth naming. There is no number on this page for how swollen is too swollen. No tape measure threshold, no percentage, no difference from the other leg that means something. Describing how to notice a change over days, which is what the section above does, is a different thing from measuring a knee, and a figure that decides whether a knee needs reviewing is for a clinician who has examined it. If you want that kind of assessment, that is what the appointment is for.
Nor is there a supplement, a diet, a drainage technique or a device recommended here, because the sources used on this page do not support one. Where you have seen a claim for any of those, ask what population it was tested in and whether anyone measured swelling. Often the answer is nobody did.
Swelling at three months, six months and a year
This is the reader almost nothing online is written for: someone four or five months out, back at work, walking fine, with a knee that still looks bigger than the other one by the evening and has quietly started to wonder whether this is permanent.
At three months, mild to moderate swelling is squarely inside what OrthoInfo describes, and the measured study above still found swelling about 11% above the preoperative level at day 90 in its 85 knees (Pua, 2015). A knee that is still puffing up at three months is on the curve, not off it.
At six months, you are at the far edge of the longest figure any patient-facing source gives, which is OrthoInfo's about 3 to 6 months for mild to moderate swelling. Some knees have settled by then and some have not, and both happen.
Past six months, the sources stop. That is the real answer, and it is better than a made-up number: there is no published figure here for us to hand you, so a knee still swelling at eight months or a year is not something this page can call normal or abnormal. It can hand you a route, though, and NICE sets one out. It expects anyone doing self-directed rehabilitation to have clear goals and a point of contact for advice and support, and it recommends supervised outpatient rehabilitation, in a group or one to one, for people who have difficulty with activities of daily living, who have ongoing problems with function, or who are not meeting their rehabilitation goals on their own (NICE NG157). A knee that is still swollen at a year, especially one that is also stiff or sore, is a good reason to use that contact rather than to keep waiting.
One addition to that, because it is not only a rehabilitation question. A knee that has stayed swollen this long, or one that had settled and has swollen up again, is worth examining and testing rather than exercising harder, so ask your surgical team to look at it as well as asking about more rehabilitation. OrthoInfo names increased pain or stiffness in a joint that had been working well among the signs of an infection around a new joint, says such an infection can appear a few months or even years after the operation, and says fever is no longer considered a sign of one. That is not a prediction about your knee, and most knees that stay puffy for a long time turn out to be doing nothing worse than taking their time. It is the reason the question gets answered by someone who can examine the knee instead of by a timeline.
One distinction matters more than all of it at this stage, so it is worth stating on its own. A knee whose swelling has been slowly decreasing for months is a different situation from a knee that had settled and has started swelling again. The second one is not the long tail of a recovery. It belongs in the next section.
When swelling needs help the same day
A few things turn swelling from a nuisance into a phone call, and the full wording for each is in the warning signs below. They are worth knowing by name, because they are the ones that expected swelling can hide behind. The warning signs after a knee replacement sorts the whole set by how fast to act, including the ones that have nothing to do with swelling.
A blood clot. This is the main reason the swelling advice exists at all, and the reason the warning has to work on a leg that was already swollen. The NHS lists having had surgery among the things that raise your risk, and notes that clots can form in the weeks afterward. Its symptoms of a clot in the leg are throbbing pain in one leg, rarely both, usually in the calf or thigh, swelling in one leg, rarely both, skin around the painful area that is red, blue or darkened and may be harder to see on brown or black skin, and swollen veins. OrthoInfo's list for a new knee adds increasing pain in the calf, tenderness or redness above or below the knee, and new or increasing swelling of the calf, ankle and foot, and asks you to tell your doctor about new or severe swelling. The one that catches people out is the trigger that is not about new swelling at all: a leg that is swelling further from one day to the next rather than settling. If you are also short of breath or have chest pain, that is emergency services, not a same-day appointment, and the first warning line below explains why.
An infection. Around a new joint this can show up early or years later, and OrthoInfo's signs include a persistent fever, chills, increasing redness, tenderness or swelling of the knee wound, drainage from the wound, and increasing knee pain with both activity and rest. Read the next sentences before you use that list to rule anything out, because they are the part a surgeon would want said first. OrthoInfo's page on infection after a joint replacement says the symptoms vary widely, from mild redness and swelling up to life threatening septic shock, that sometimes there are no symptoms at all, and that fever is no longer considered a sign of an infection after a joint replacement. The same page names wound drainage, usually more than ten days after surgery, and increased pain or stiffness in a joint that had been working well. So a normal temperature is not an all clear, and neither is a knee that has never gone red. The late version is the one people do not expect, so it has a warning line of its own below.
Bleeding into the joint. The ordinary pattern is a knee that swells over days and then settles over weeks. A knee that goes tight and tense over a few hours, or one whose wound starts to bleed, is a different event, and it is likelier while you are on medicine to lower your clot risk: the NHS names bleeding from the surgical wound among the serious side effects of those medicines. This is the one place on this page where comparing one morning with the next does not apply, because the comparison costs you a night. Same day, and the line below says it in full.
The tendon at the front of the knee, which is the one nobody expects to meet on a swelling page. A knee that suddenly swells and will not straighten, or a leg you can no longer lift out straight when you could the day before, is a different event again, and no fall is needed for it. Sometimes there is a pop or a tearing feeling with it, and sometimes a dip you can feel just above or just below the kneecap. OrthoInfo's page on patellar tendon tear names an inability to straighten the knee and an indentation at the bottom of the kneecap among the signs, and says a repair done soon after the injury does better than a late one, which is why the line below asks for the same day and for your weight kept off the leg.
The wound. A wound that becomes more red, hot, swollen or painful, that starts leaking, that is still leaking in the second week, or that is coming apart at the edges is a same-day matter, and so is a temperature with it.
And one that is not about the swelling but can arrive with it. New numbness, tingling or burning in the lower leg or foot, beyond the numb patch of skin around the scar, needs advice the same day. If the foot or the toes turn cold, pale, blue or gray, that is emergency services or an emergency department straight away, and you should not drive yourself. The line below says it in full.
One on this list is slower than the rest, and it is the one people save for an appointment that is weeks away. A knee whose bending or straightening has stopped improving from week to week, or that is getting stiffer, goes to your physio or surgical team within the next few days instead. A stiff knee is easier to free up early than late, and the line below carries the timing and the source for why the date you raise it matters.
If you take one thing from this page, take these two sentences together. Months of swelling after a knee replacement is normal and expected. And expected swelling is exactly the cover a clot or an infection needs, which is why the direction of travel, day to day and week to week, and how fast it is moving, are what to watch, not the swelling itself.
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: your knee goes tight, tense and much more swollen over a few hours rather than over days, the swelling suddenly makes it harder to bend or straighten than it was yesterday, or the wound starts to bleed. Contact your surgical team or get medical advice the same day, and do not wait for tomorrow morning to compare it. Bleeding into a new knee joint can swell it this fast, it is more likely while you are taking tablets or having injections to lower your clot risk, and the NHS names bleeding from the surgical wound among the serious side effects of those medicines. Go to an emergency department if the bleeding will not stop, the pain is severe, or you feel faint.
- 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: 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: 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: 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.
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.
- Routine: swelling in your new knee that has not settled by about six months, or swelling that comes back after the knee had settled down. This is not an emergency, but ask your surgical team for a review rather than deciding for yourself whether it is normal, because a knee that stays swollen or swells up again is examined and tested, not judged from a web page. OrthoInfo names increased pain or stiffness in a joint that had been working well among the signs of an infection around a new joint, says the signs can be as little as mild redness and swelling, and says fever is no longer considered a sign of one. Get medical advice the same day instead, not a routine appointment, if the knee also becomes hot or red, the pain keeps building while you are resting, the wound is leaking, or you have a high temperature or feel hot, cold or shivery.
Common questions
How long does swelling last after a knee replacement?
Months. OrthoInfo, which writes patient information for the American Academy of Orthopaedic Surgeons, puts the worst of it in the first few days or weeks and then describes mild to moderate swelling lasting about 3 to 6 months after the operation. Those are figures for a population and not a prediction about your knee. If you want a measured picture of the fall rather than an end date, one study followed 85 knees after a single knee replacement and found swelling about 35% above the level before surgery on day 1 and still about 11% above it on day 90 (Pua, 2015), which is the long tail most people are not warned about.
How do I get rid of swelling after a knee replacement?
You manage it rather than get rid of it, and three ordinary things do most of the work. The NHS asks you to keep the leg raised as much as possible and not to stand for long periods, which it says can cause swelling in your ankles. OrthoInfo asks for the leg to be elevated with ice applied, and notes that compression stockings may also help. And moving the foot and ankle is encouraged straight after surgery, both to help prevent leg swelling and to keep clots from forming (OrthoInfo). When you raise the leg, support it from the thigh to the heel with the knee straight, not propped on a pillow underneath the knee, which the NHS tells you not to do. Anything beyond that, including any compression garment or cooling device, is a question for your own team rather than a purchase.
Does swelling mean I have done too much?
Often, but not always, and the exception is the part that matters. A knee that is noticeably more swollen and stiffer the next morning than it was the morning before usually means the session was bigger than the knee was ready for, and dropping back a step is the usual answer. What you cannot do is treat swelling as a training signal every time, because an infection around the new joint shows up the same way: more swelling, more pain. If the knee is also hot or red, if the pain keeps building while you are resting and not only while you move, if you have a temperature or feel hot, cold or shivery, or if the leg is swelling further from one day to the next, that is a same-day call to your surgical team and not a change to your exercises. A normal temperature does not rule it out, because OrthoInfo says fever is no longer considered a sign of an infection after a joint replacement. Nor does the speed: a knee that goes tight and tense over a few hours is its own same-day call, and not something to compare with tomorrow morning. The warning signs below set out which route to use.
How long do I wear the compression stockings?
As long as your team says, and the usual answer is longer than people expect. The NHS's instruction is to wear them at all times and only take them off to wash them, and it says most people have to wear them for at least 6 weeks. They are given to lower the risk of a blood clot, and OrthoInfo adds that they may also help with swelling. Two things people are rarely told: finishing your clot tablets or injections does not mean the risk has gone, which is part of why the stockings run on, and if a stocking feels too tight, rolls down, digs in or will not go on over a swollen leg, that is a conversation with your team, not a reason to stop wearing it.
Should I be worried if my knee is still swelling at six months or a year?
It is worth having looked at rather than worried about, and it is not something to judge from a web page. The patient-facing sources stop giving figures after about 6 months, so there is no published number to compare yourself with past that point and this page will not invent one. There is a route instead. NICE expects anyone doing their own rehabilitation to know their goals and to have someone to contact for advice, and it recommends supervised outpatient rehabilitation for people who are struggling with everyday activities, who still have problems with function, or who are not meeting their goals on their own (NICE NG157). Ask your surgical team to examine it as well, not only your rehabilitation contact, because a knee that stays swollen that long is examined and tested rather than judged against a figure, and OrthoInfo names increased pain or stiffness in a joint that had been working well among the signs of an infection around a new joint, which can appear months or years later and without a fever. A knee that had settled and has started swelling again, or one that is hot, red or increasingly painful, is a different matter and is in the warning signs below.
References
- American Academy of Orthopaedic Surgeons. Total knee replacement. OrthoInfo. https://www.orthoinfo.org/en/treatment/total-knee-replacement/
- American Academy of Orthopaedic Surgeons. Activities after total knee replacement. OrthoInfo. https://www.orthoinfo.org/en/recovery/activities-after-knee-replacement/
- American Academy of Orthopaedic Surgeons. Infection after joint replacement. OrthoInfo. https://www.orthoinfo.org/en/diseases--conditions/joint-replacement-infection/
- American Academy of Orthopaedic Surgeons. Patellar tendon tear. OrthoInfo. https://www.orthoinfo.org/en/diseases--conditions/patellar-tendon-tear/
- Hosanee S, Elebo N, Sikhauli N, Pietrzak JRT. Reluctant knee: understanding and managing stiffness after total knee arthroplasty. International Orthopaedics. 2026;50(9):2337-2346. https://doi.org/10.1007/s00264-026-06905-0
- NHS. Recovering from a knee replacement. Page last reviewed 9 September 2026. https://www.nhs.uk/tests-and-treatments/knee-replacement/recovery/
- South Tees Hospitals NHS Foundation Trust. Post total knee replacement management. Patient information, 26 February 2025. https://www.southtees.nhs.uk/resources/post-total-knee-replacement-management/
- National Institute for Health and Care Excellence. Joint replacement (primary): hip, knee and shoulder. NICE guideline NG157. Published 4 June 2020. https://www.nice.org.uk/guidance/ng157
- NHS. DVT (deep vein thrombosis). Page last reviewed 30 April 2026. https://www.nhs.uk/conditions/deep-vein-thrombosis-dvt/
- Pua YH. The time course of knee swelling post total knee arthroplasty and its associations with quadriceps strength and gait speed. Journal of Arthroplasty. 2015;30(7):1215-1219. https://doi.org/10.1016/j.arth.2015.02.010
- Lee Y, Shin YS, Kim HJ, An J. Effectiveness and methods of cryotherapy in reducing swelling after total knee arthroplasty: a systematic review on randomized controlled trials. Nursing Open. 2023;10(9):5989-5998. https://doi.org/10.1002/nop2.1906
- Liang Z, Ding Z, Wang D, Guo Y, Zhu L, Luo Z, Li L. Cryotherapy for rehabilitation after total knee arthroplasty: a comprehensive systematic review and meta-analysis. Orthopaedic Surgery. 2024;16(12):2897-2915. https://doi.org/10.1111/os.14266
- Liu MM, Tian M, Luo C, Wang S, Shao L. Continuous cryotherapy vs. traditional cryotherapy after total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials. Frontiers in Surgery. 2023;9:1073288. https://doi.org/10.3389/fsurg.2022.1073288
- NHS. Anticoagulant medicines. Page last reviewed 9 September 2024. https://www.nhs.uk/conditions/anticoagulant-medicines/
- NHS. Rivaroxaban. Page last reviewed 5 August 2026. https://www.nhs.uk/medicines/rivaroxaban/
- Arthritis UK (formerly Versus Arthritis). Knee replacement surgery. https://www.arthritis-uk.org/information-and-support/understanding-arthritis/arthritis-treatments/surgery/knee-replacement-surgery/
- NHS. Sepsis. Page last reviewed 14 May 2026. https://www.nhs.uk/conditions/sepsis/
- NHS. Falls. https://www.nhs.uk/conditions/falls/
- NHS. Low blood pressure (hypotension). Page last reviewed 11 July 2023. https://www.nhs.uk/conditions/low-blood-pressure-hypotension/
- NHS. Fainting. https://www.nhs.uk/symptoms/fainting/
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.