Swelling after knee surgery is a rather common, normal finding.  Many patients ask me if their swelling is normal, how long will it last, and is it dangerous?   These are all great questions.

Swollen-KneeFirst, let’s understand what swelling is and why it happens. Swelling can mean more than one thing. The development of fluid in a knee joint, in doctor-speak called an ‘effusion’. This is not the same as swelling in the tissues around your knee or in your leg.  Swelling occurs as a natural part of the inflammatory response to injury.  There may be very little after a simple procedure like a knee arthroscopy, or more swelling after a joint replacement.

After a knee scope, or arthroscopy, it is common to have swelling, or an effusion, in the joint for a few days, or sometimes, as long as a few weeks. Patients with arthritis tend to be swollen longer.  Patients that have a knee replacement surgery can have knee swelling, or a knee effusion as we call it, that lasts for months.

After a big knee surgery like a ligament repair or replacement, you may have some of both – fluid in the knee joint (effusion) and swelling in the leg.  This often lasts for several weeks.  Sometimes, I see people that are still swollen several months later (without any pain) and I believe this can be normal – everyone is different.

What does knee swelling look like ?

Knee Effusion

Ultrasound image of fluid in the knee joint

Knee swelling in the joint, or a knee effusion, is rather easy to see on ultrasound.  It looks like a large black area on the image that can be moved around.  Here is a picture from a recent patient of mine showing a large joint effusion.  The arrows show you the edge of the tissue above the swelling, and the lower white line is the front of the femur bone.  The fluid is sitting in between the two.

Is knee swelling dangerous after surgery?

It is normal to have some swelling after surgery.  Don’t be alarmed.  There can be bruising as well and discoloration of the skin.  This will resolve with time and does not need to be alarming.  If you are worried, please come in and see me in the office to check.

How to reduce swelling after surgery

Compression stockings

There are several simple things you can do. First, wear a pair of ‘TED’ hose, or compression stockings. This will help to literally ‘squeeze’ the fluid out of your legs and feet. You can wear these almost 24 hours a day.


Keep your leg up and elevated. The higher the better. This will help to drain fluid out of your leg.  Try using a few pillows under your calf.  Get it above your heart.


PolarCare Ice MachineIce your knee. This can be done with ice packs, or with an ice machine – a special pad and a pump that circulates cold water through the pad like the one shown here. The cold helps to reduce inflammation which will decrease the swelling and effusion.

Ibuprofen / Naproxen or other anti-inflammatory medicine

These medicines work to stop inflammation and thereby reduce the swelling after surgery. I often suggest 600-800mg of ibuprofen 3 times a day, or 440mg of naproxen (Aleve) twice a day.  Be sure to check to see if this is something you are allowed to take after surgery.  Patients on strong blood thinners should not take any anti-inflammatories.

I’ve put a number of products that I’ve seen help patients with knee swelling on my related products page.  I don’t sell these but refer you to amazon to find them.  Click here to shop.

Patients ask a lot of questions about swelling – feel free to ask me below if you have some of these questions and I’ll try to answer them for you.  I want you to understand what knee swelling means and when it is important to see your doctor.

Please don’t take this all as direct patient advice.  I am happy to see you in my San Diego, California office OR if you are from out of town or the country, I continue to do telemedicine visits.  Contact me to set this up.  I look forward to meeting you.

I have many blog posts like this one about orthopedics, regenerative medicine, surgery, robotics and more.   Check out the menu toward the bottom of the page in the BLOG section, or more common situations under ‘CONDITIONS‘ and ‘TREATMENTS’.  Also, feel free to comment below.