Why is there so Much Pain After Knee Replacement?

Did you recently have a knee prosthesis surgery (knee replacement) and you’re experiencing pain? Are you wondering how long the pain will last or if it’s a sign of a problem?

Or maybe you’re just looking for ways to relieve the pain?

Well, look no further because I’m a physiotherapist who deals with people who have these same questions every week. Often, after surgery, the hospital stay is short and healthcare professionals are in a rush, so we don’t get to ask all our questions.

But fear not, I’m here to answer all the questions you might have!

I’ll share my professional experience and knowledge from various studies conducted internationally on people who have undergone knee replacement, just like you.

And the best part? These tips apply whether you have a total / full knee arthroplasty (TKA or TKR) or a unicompartmental / partial knee prosthesis (UKP) (also known as knee arthroplasty or knee replacement, it’s the same thing).

All the references for the studies I rely on are listed at the end of this article.

Enjoy your reading!

Last update: September 2023
Disclaimer: Amazon affiliate links
Written by Nelly Darbois, physical therapist and scientific writer

Why does my knee replacement hurt so much?

Why does a knee hurt after surgery?

To install a knee prosthesis, the surgeon made an incision in the skin, as well as through various layers and types of tissue beneath the skin (fascia, bone tissue, etc.).

These tissues need to heal to become functional again.

Your body, your immune system (defense system), reacts accordingly, automatically. Inflammatory reactions occur in the knee after the replacement surgery.

This inflammation causes:

• an accumulation of fluids in the various layers of tissue. That’s why your knee swells after a replacement and edema appears;
• pain (especially at night);
• redness, warmth in the knee area;
• one or more hematomas and bruises.

This inflammation is a necessary step and is beneficial in the medium and long term! It’s what allows damaged tissues to be repaired.

It brings all the necessary substances to the damaged area via fluids to help the damaged structures heal naturally as quickly as possible.

The inflammation that causes swelling is actually a good thing, it’s therapeutic! It’s an automatic reaction of our immune system, inherited from our ancestors. This inflammation helps repair damaged tissues.

Also, we’re not all equal when it comes to pain. Some people may naturally tend to be more concerned about their health and feel more pain after surgery than others (Birch 2019).

Keep in mind that knee orthopedic surgeries are known to be among the most painful surgeries (Schindler 2022).

Therefore, pain after a knee prosthesis is mainly due to inflammation. And this inflammation is normal and even beneficial for tissue healing.

What are the typical types of pain following knee replacement surgery?

Pain is almost always present after knee replacement surgery. Sometimes it appears a few hours after the operation.

Often, it is at its maximum when people return home: the anesthesia medications are no longer effective, and there is stress about going home without medical assistance (even though it is also a relief)!

In the hospital, you may have had analgesics in infusion, subcutaneous injection, or a femoral block. These are powerful and effective treatments for pain (Cochrane 2014a). However, they no longer have an effect when you return home.

Pain can be located:

• behind the knee; in front of the knee, at the level of the incision;
• all over the knee;
• radiating into the thigh or leg.

They also occur at different times (or are sometimes continuous). They can be mild or very intense. We are not all equal when it comes to pain, and our bodies do not react in the same way.

Having very severe pain does not necessarily mean that you will take longer to recover or that you will recover less well.

One of my current patients has only taken 3 medication tablets (and only paracetamol) since his total knee replacement (TKR) surgery 3 weeks ago. He has some pain, but it is largely tolerable. He walks 300 meters every day in his neighborhood, goes up and down stairs.

In contrast, another of my current patients who also had a TKR 3 weeks ago is forced to take morphine due to pain, particularly at night.

Total knee replacement pain at night

The most common pain occurs at night, which is typical of inflammatory pain.

They can wake you up, usually towards the end of the night, and can be a source of anxiety, even though they are a “normal” manifestation of your body.

Later in the article, we will see that there are certain things that can be put in place to relieve them.

Pain while moving

People who have knee surgery often experience pain in the morning upon waking up. The logical explanation is that the knee has been in the same position for a good part of the night. Due to inflammation, it is less flexible than usual.

Hence the pain when it is put back into action, when it is unfolded or folded more, when the muscles surrounding it contract.

The same thing happens during the day when changing positions or putting weight on it, for example when walking.

Although these pains are certainly annoying, they are not a sign of a problem, at least not as long as they are not accompanied by other symptoms such as fever or a scar with significant yellowish discharge.

Pain at rest during the day

In some people, pain also occurs during the day, at rest, without doing anything in particular. They can “shoot” or pulse, which is again typical of inflammatory pain.

We will see how long these pains usually last and how to relieve them.

After knee replacement, pain can occur at night or during changes in position during the day, or even without doing anything in particular.

How long do the pains after knee replacement surgery last?

Here’s the typical evolution of pain after a knee replacement surgery.

What is the most painful time after knee replacement surgery?

Pain is at its maximum the day after surgery after knee replacement surgery (5.8/10 on day 1).

• Pain steadily decreases during the first week (down to an average of 4.6 on day 8).
• On the 9th day, pain increases again.
• Then, pain steadily decreases again.
• 30 days after surgery, it averages at 3/10.

Source : Schindler 2022

This doesn’t mean that your experience will be exactly the same. These are average data taken from a large number of patients (but a small number compared to the number of people who undergo knee replacement surgery every year!).

Total knee replacement pain duration

Of course, there can be a lot of variability when it comes to pain. These numbers are a trend of what to expect.

But there will be people at both extremes who will experience very different things (no pain at all, or low pain that increases, or pain that fluctuates every day…).

What can we deduce from this?

• That pain can fluctuate (decrease then re-increase).
• That it still tends to improve over the weeks.

Know that one year after the surgery, 1 in 5 people still have knee pain. It’s annoying, but it’s not a sign of anything serious, like a problem with the prosthesis. (Larsen 2021) The pain, however, is usually low: rated on average at 1.2/10. (Wang 2022)

Also, 10 to 20% of people are dissatisfied with the operation, even if it has resolved the initial problem related to arthritis. This is largely due to the sometimes difficult-to-manage pain. (Schindler 2022)

How can we find relief for post-surgery knee pain?

Here are some simple solutions that you can try to relieve your knee pain after knee replacement.

Natural remedies for knee pain after knee replacement

Some of these solutions have been tested in clinical studies, and few side effects have been reported. Some people are partially relieved by these treatments, while others are not:

• ✅ Apply cold to your knee (see on Amazon). You can buy cold packs to put in the freezer, or simply use a bag of frozen peas, which will mold well to the shape of your knee. Be sure to always put something between the cold element and your skin to avoid burning yourself. You can use cold as often as you want, including at night.
• ✅ Change your position regularly.
• ✅ Be as active as possible. Exercise releases hormones (such as endorphins) that have a beneficial effect on pain. There is no dangerous exercise after a knee replacement! See my eBook on knee replacement for more ideas of exercise
• ✅ Find a comfortable position for your knee by propping it up with pillows. Some people find relief by placing pillows under their knee so that it is not completely straight. This can be done at certain times of the day, but you should avoid spending too much time with your knee bent in this way, as it can become stiff and difficult to straighten later on.
• ✅ Massage your thigh or the parts of your leg that are sore. Massage has a very short-term effect, only on the moment. And some people are not receptive to it at all. There is no “right” massage technique, what matters is that you manage to relieve yourself a little through touch. Like with cold, the effect quickly fades away afterwards.

See also: Does CBD work for knee arthritis and pain?

Medication for knee pain

Your surgeon will also have likely prescribed pain medications for you. Several of them.

• Systematically: to take even before the pain appears
• On demand: if you are in pain. You may also take them at night.

It can be as simple as paracetamol, or stronger medications, up to morphine, opioids (although it is not certain that the latter are more effective on pain after a TKR, especially given the risks (Shah 2020)).

It is very difficult to recommend one medication management over another. Professional prescribing habits vary widely.

For example, in just one hospital in the Netherlands, a research team found that for 301 people who had undergone knee arthroplasty, 35 different combinations of medications had been used! (Thijssen 2022)

From my experience, some people hardly take any painkillers. Others take them for a few days and then quickly reduce the dosage. And others will need them for longer, as their inflammation lasts longer.

It’s possible to check back in with your doctor a few weeks after the surgery to see if there’s a more suitable medication for you, if the pain persists.

Several tested treatments don’t have impact on knee pain

Several tested treatments don’t have a significant impact on pain on average, in people who use them. This means that pain was roughly the same in patients who had these treatments and those who didn’t:

• ❌ Mobilizing the knee in the hospital or with a physiotherapist using an continuous passive motion (often called Kinétec, after the brand that sells it). It’s an electric device that bends and stretches the knee. You adjust it with a lever. (Cochrane b 2014);
• ❌ Having many sessions of physiotherapy (Orndhal 2021);
• ❌ Using pressotherapy. This involves putting the leg in a kind of boot that compresses and releases. Surgeons sometimes prescribe this for rental, or physiotherapy practices have the equipment. But this doesn’t have a significant impact on pain or swelling (Christensen 2021).
• ❌Motor imagery, lymphatic drainage, and kinesio-taping are treatments that have been tested in studies of too poor quality to draw any conclusions.

Some teams also recommend that patients keep a semi-rigid brace with the knee extended for the first 8 days following the operation. According to the results of a study involving 72 patients, pain is less severe, and medium- to long-term flexion is better in people who have had this brace compared to those who didn’t.

However, this is a practice that I have never seen in France, where early mobilization of the knee in flexion is encouraged. (Kaseb 2022)

Ice, a comfortable position, regular changes of position, staying active, self-massage, and taking pain-relieving medications are the main simple ways to relieve pain after knee replacement surgery.

When should we be concerned about our knee pain?

You may have searched for information on forums, on the internet, on success rates of knee replacements. Perhaps you’re afraid that your pain might be a sign of a problem, a failure of the operation.

Or maybe you’re wondering when to start worrying about this pain, when is it no longer normal to have pain? 1 month? 3 months? 4 months? 6 months?

There is no “deadline”. As you have seen in the previous sections, some people experience pain several months after the operation, even if the prosthesis is well in place and there is no complication or failure of the prosthesis.

Of course, this does not mean that you have to resign yourself to being in pain for the rest of your life!

Whatever the timing of the pain, discuss it with the healthcare professionals who are following you at that time: usually, at least a physiotherapist and a nurse. Get their professional advice.

They are used to taking care of people in your situation, and know how to spot signs of worry, which are generally not just pain (but rather signs of infection or phlebitis).

In any case, you will review your progress with your surgeon about 1 and a half to 2 months after the operation (in France). Some surgeons will also tell you not to hesitate to call their secretary if you have any concerns; others will recommend that you go through your regular doctor.