Swelling After Knee Surgery: What Is Normal and When to Call a Doctor

A few days after knee surgery, many people look at a knee that is bigger, warmer and more colorful than expected and wonder whether everything is all right. Most of the time it is: swelling, bruising and some warmth are part of how the body heals after an operation. Here is what is usually normal, what helps and when to call your doctor straight away. Your surgeon's protocol always comes first, and recovery differs from person to person.

Why the knee swells after surgery

After an operation, the body sends extra blood and fluid to the area, and some blood from the operation itself collects under the skin and inside the joint. That is why the knee looks puffy, feels tight and warm and is often bruised. The amount depends a lot on the procedure: a short arthroscopy usually causes far less swelling than a ligament reconstruction or a knee replacement. Other causes of swelling are covered in our article on a swollen knee.

A rough timeline

Hospitals give different numbers, so read this table as a range, not a promise.

When	What is common
First 3 days	Swelling often increases rather than decreases. The knee feels tight, warm and hard to bend.
First 2 weeks	Bruising can spread down the leg to the ankle, and its color changes from purple to green and yellow. Mild warmth and a little redness around the wounds are common.
Up to about 6 weeks	After a simple arthroscopy, swelling usually settles gradually.
After 6 weeks	After a knee replacement or ligament surgery, some swelling and warmth after activity can last months, sometimes up to a year.

The direction matters more than the exact day: a knee that slowly gets better from day to day is on the right track.

Ice and elevation: what usually helps

• rest with the leg raised on pillows, with the heel higher than the knee,
• put the pillows under the calf and heel, not only under the knee, so the knee can still straighten fully,
• cool the knee if your hospital recommends it, usually up to 15 to 20 minutes at a time, wrapped in a cloth and never directly on the skin,
• move the ankle up and down often and gently tighten the thigh muscles,
• spread activity over the day: short walks more often rather than one long outing that leaves the knee puffy by evening,
• wear compression stockings only as your hospital tells you; some hospitals give them to lower the risk of blood clots.

Cooling suits most people in the first days. Later, some prefer gentle warmth for stiffness, but not on a knee that is still hot and swollen. Our article on heat or cold for knee pain explains the difference.

Stiffness and losing the bend

Swelling and stiffness go together: a joint full of fluid does not want to bend. Some stiffness is normal, especially in the morning or after sitting, and after a knee replacement mild stiffness can last for months. The first thing to watch is straightening: if the knee stays slightly bent for a long time, walking gets harder later, so many hospitals advise against a pillow under the knee for hours. The second thing is bending: your physiotherapy exercises, done little and often without forcing, are usually the most important part of the day. If the knee bends less instead of more, stops making progress even though you exercise regularly, or you cannot tighten the thigh muscle, tell your surgeon or physiotherapist early. Stiffness caused by scar tissue is easier to treat when it is found early.

What surprises many people

In patient forums the same experiences come up again and again:

• the swelling comes back by evening or after physiotherapy, even though the knee looked almost normal in the morning,
• the bruise moves down the leg and shows up near the ankle a few days after the operation,
• the knee stays a little warmer than the other one for days, and after a knee replacement sometimes for months,
• ice feels pleasant but does not make the swelling disappear, so people wonder whether they are doing something wrong,
• recovery is slower than friends or the internet suggested, and following how others recover mostly brings worry.

When to call your doctor

Contact your surgeon, the hospital or your doctor the same day if:

• the wound becomes more and more red, hot or painful, or leaks cloudy fluid with an unpleasant smell,
• you have a fever or chills,
• pain or swelling gets clearly worse instead of slowly better, also at rest,
• the calf on one leg becomes swollen, painful, warm or red, which can be a sign of a blood clot in a deep vein,
• the swelling has not improved at all after about a month, or the knee is hot and clearly redder than the other one.

Call emergency services straight away if you suddenly find it hard to breathe or have chest pain, especially when breathing in or coughing. A blood clot can travel to the lungs, and this needs urgent treatment. Clots are more likely after surgery and when you move less, so use clot-prevention medicines or stockings exactly as prescribed.

Where a knee sleeve fits in

A knee sleeve is not a treatment for swelling after surgery and does not speed up recovery. It is never worn over fresh wounds, and in the first days the hospital's plan, any prescribed stockings or brace and physiotherapy come first. Later, when the wounds have fully closed and your surgeon agrees that light compression suits you, a soft bamboo knee sleeve can give the knee a pleasant feeling of warmth and support, for example on the first longer walks. If the knee becomes more swollen, numb or painful while you wear it, take it off. More on the first weeks: our guide to recovery after knee arthroscopy.

A sleeve you will actually wear

The best sleeve is the one that does not end up in a drawer. The KeenTrove Bamboo Knee Sleeve is made for exactly that:

• soft, breathable bamboo, comfortable even in summer
• fits snugly but does not dig in behind the knee
• does not lock the knee, so you move naturally
• wear it under your clothes during the day and in bed at night

With 60 days to get your money back, you have nothing to lose.

See the bamboo knee sleeve →

Note: this article is for information only and does not replace an examination by a doctor. If you have circulation problems or diabetes, or have recently had knee surgery, talk to your doctor before wearing compression.