Swelling after a knee replacement usually lasts about 3 to 6 MONTHS.
Mild to moderate swelling for that long is expected, according to the American Academy of Orthopaedic Surgeons. A little puffiness after a busy day can hang around for longer.
It often gets WORSE before it gets better. Many people find swelling builds over the first few weeks and peaks around four to six weeks, just as they start doing more.
Normal swelling goes up and down with your day: bigger in the evening, smaller in the morning. Swelling that only goes up, or comes with a hot, painful calf, a red wound or a fever, is not the normal kind.
What normal swelling looks like
- The whole leg, not just the knee. Fluid drains downhill, so the shin, ankle and foot often swell too, sometimes more than the knee
- Bruising that travels. Purple and yellow patches can appear down the shin and even into the foot days after surgery. This is old blood moving with gravity
- Warmth. A new knee feels warmer than the other one for months. Warm on its own is expected
- A tight, full feeling when you bend. Swelling takes up space inside the joint, so it physically limits bend. As the swelling goes down, bend usually comes up. See stiff knee after knee replacement
- Slim at 8am, puffy at 6pm. The daily rise and fall is normal, for months
Why it swells
Surgery on a big joint causes bleeding and inflammation around it.
Your body sends fluid to the area as part of healing. In the early weeks you also walk less, and the calf muscle is what normally pumps fluid back up the leg. Less walking means less pumping, and gravity wins.
What helps
- Elevate properly. Lie down with pillows under the calf and heel so the foot is above the knee and the knee is above the hip. A footstool while sitting is only a little help. A spell lying down with the leg up, a few times a day, does far more
- Never a pillow bent under the knee. It feels comfortable and trains the knee to stay bent
- Ice for up to 20 minutes, with a thin towel between the ice and your skin. Check the skin, especially if you have numb patches around the scar. Many people find it most useful after exercise
- Ankle pumps. Point and pull the foot for a couple of minutes, several times an hour. Your calf muscle is a pump. Use it
- Walk little and often. Several short walks beat one long one
- Compression. If your surgeon prescribed stockings, wear them as instructed. They are mainly there to reduce clot risk. For swelling on its own, trials have not shown a clear benefit, so don’t rely on it
- Keep up your exercises. Moving the knee helps clear the swelling. See exercises after knee replacement
Swelling is the knee’s report on yesterday. Read it every morning.
Pacing: the morning check
Most swelling problems are pacing problems. The knee does not complain during a long day in the garden. It complains the next morning.
- Check first thing: compare the knee, shin and ankle with the morning before
- About the same or better: you got the amount right. Keep going, and add a little
- Noticeably bigger, hotter or sorer: you did too much. Cut back for a day or two, don’t stop moving
- Build in lying-down time on busy days rather than waiting until the leg is already tight
- Standing still is worse than walking. Long spells at the kitchen counter or standing in line make the ankle balloon. Keep shifting weight or sit with the leg up
Normal swelling, clot or infection?
Normal swelling is annoying. Two things that can look like it are serious.
- Normal: goes up in the evening and down overnight, improves with lying down and elevation, slowly getting better week to week
- A blood clot in the leg (DVT): a new or increasing swelling of the calf, ankle and foot, often with a painful, tender calf, sometimes red or warm. The risk is highest in the first few weeks after surgery. See blood clot after surgery
- Infection: the knee becomes hotter, redder, more swollen AND more painful, often with a wound that drains, fever or chills. It can happen weeks or even months after surgery
The difference is the direction. Normal swelling goes up and down. Trouble tends to keep climbing, and brings pain with it.
For the full picture of recovery around swelling, see knee replacement recovery week by week.
Call your surgeon today if
- Your calf is painful, tender or newly swollen, especially on one side
- The wound is red, spreading, weeping or draining
- You have a fever or chills
- The knee is getting hotter, redder and more painful at rest as well as with activity
- Swelling keeps rising for several days despite rest and elevation
A knee infection does not always come with a fever. Don’t let a normal temperature talk you out of calling about a knee that’s getting worse.
Go to the emergency department or call emergency services if
- You are suddenly short of breath
- You have chest pain, especially pain that is worse when you breathe in or cough
- You are coughing up blood
These can be signs that a clot has traveled to the lung.
Mention it at your next review if
- Swelling is stopping you from bending the knee past about 90 degrees
- The knee is still clearly swollen beyond about six months
- The swelling is making it hard to sleep or wear shoes
- You’re unsure whether your stockings or ice routine are helping
Swelling that goes up and down is healing. Swelling that only goes up needs a phone call.