How safe is total knee replacement surgery?

Doctor's Answers 2

Photo of Dr Alan Cheung
Dr Alan Cheung

Orthopaedic Surgeon

Thanks for the question which I think is a good one. Often patients who ask this question are answered with a barrage of statistics and percentages which is confusing.

As someone whose mother recently underwent a total knee replacement (TKR) I understand that what patients are really looking for in a surgeon when they ask this question, is someone who can

  1. do the best surgery possible,
  2. communicate and empathise well, and
  3. will care for their family member as if they were their own, which is something I strive for.

The short answer to your question is that – yes, total knee replacement surgery is generally safe, but it depends upon the person having surgery.

Every human being is different and reacts differently to an operation. If your father has a lot of underlying medical problems then that may increase his risk of complications during and after surgery. That is why it is important to find a doctor who treats your father as an individual, rather than having a ‘one size fits all’ approach.

A good doctor will take a careful history asking about underlying medical problems, and perform a thorough examination, not just on the knee, but also of the heart, lungs and abdomen if relevant.

He or she should be able to take the time to explain the procedure and potential complications in understandable language, as well as answer your and your father’s questions. This is the ideal scenario, but I understand that in a busy clinic sometimes it can be difficult for doctors to do so.


Before your surgery, your surgeon and anaesthetist should make a risk assessment of your father’s fitness for surgery and may decide whether he is a normal healthy patient, or someone who has a mild/severe disease.

They will look at any underlying medical problems related to each organ system – e.g. heart, lungs, blood vessels, liver, and may organise further investigations and refer to a particular specialist if there is a problem.

Once all medical problems have been addressed, the anaesthetist will discuss with your father what he thinks is the safest anaesthetic to use. In the operating theatre many precautions are taken to minimise risk of infection.

After the surgery your father will be given antibiotics via a drip, and measures will be taken to reduce his risk of developing a ‘blood clot’ in his legs or lungs. He will be given strong painkillers which may enable him to stand and walk immediately after the procedure. If your father is at higher risk of complications then he may be observed closely in a High Dependency Unit (HDU) overnight.

With regards to specific complications, infection is perhaps the most feared complication following TKR.


Fortunately the rate of deep joint infection following TKR is low (less than 1%). There are many risk factors for infection, and a good surgeon will try and control/optimise these factors to reduce risk of infection.

A recent study from Cornell University in the USA1 looked at nearly 18000 patients undergoing TKR and the risk factors for infection. They found that patients with liver, lung or kidney disease, undergoing blood transfusion or having a urine infection in hospital increased the risk of joint infection.

Diabetes mellitus, rheumatoid arthritis, smoking, obesity have also all been identified as potential risk factors for joint infection and should be addressed prior to surgery.


A blood clot in the deep veins of the legs is called a deep vein thrombosis or “DVT” and can occur following a surgical procedure such as a TKR. Rarely, a DVT can travel to the lungs and form a “PE” or pulmonary embolism which can be life threatening.

Fortunately PE’s are not common and occur in only around 1% of patients. The risk of DVT and PE can be reduced through the use of certain ‘blood thinning’ medicines and/or mechanical devices such as foot pumps. Early walking and mobilisation following surgery may also be important, which is why I prepare my patients to walk immediately following surgery and avoid resting in bed for long periods.2


If a patient has liver disease, low platelet count (cells that help the blood clotting process), or clotting abnormalities, then they will be at higher risk of bleeding following surgery and may need a blood product transfusion.

Some patients are already on blood thinning medicine such as clopidogrel or warfarin and will need to stop these 10-14 days before surgery. If your father is a follower of TCM then he should avoid taking TCM herbal medicine for at least 2 weeks prior to any operation.

Cordyceps (冬虫夏草) in particular may increase risk of bleeding. Other Chinese herbs which have blood thinning effects include Szechwan lovage rhizome (chuanxiong), radix salviae miltiorrhizae (danshen), safflower (honghua), red peony root (chishao) and motherwort herb (yimucao).


In summary, total knee replacement is a very common and effective surgery performed worldwide to replace worn out joints, and is generally safe and well tolerated. As each person has a different medical history and response to surgery, its best to find a surgeon who will treat your father as an individual and not take a ‘one size fits all’ approach.

Complications can never be completely eliminated, but with a careful risk assessment and modern techniques, they can be minimised. I hope all goes well with your Father’s operation, thanks for asking your question.

Dr Alan Cheung


  1. Poultsides LA et al. Infection risk assessment in patients undergoing primary total knee arthroplasty. Int Orthop.2018 Jan;42(1):87-94.
Photo of Dr Henry Chan
Dr Henry Chan

Orthopaedic Surgeon

This is a common question who is asked by everybody suffering from severe osteoarthritis of the knees.

Total knee replacement surgery is very safe, and the success rate is well over 97-98%. But of course, like any other surgery, there are several potential risks that I will always highlight to my patients.

1. Infection (< 1%): I’d say this is the ONE complication that is beyond the control of the surgeon. Despite the advancement in medical technology, bacteria remains to be our top enemy to our health. Fortunately, the risk of deep infection is very low (< 1%) which is the international standard for all reputable joint replacement centres in the world.

  1. Neurovascular injury (injury to the nerve or the blood vessels, < 1%): This is the most dreaded complication. However, with proper protection and meticulous surgical technique, the risk of such complication can be even lower than 1% in experienced hands. With the help of the robot, which has a mechanism to protect the nerve and the blood vessels, we aim to bring down such complications to ZERO.

3. Anaesthesia risk (<1% if you are healthy and not suffering from any major problems with the hearts/ lungs/ kidneys/ stroke): Total knee replacement is not a small procedure that can be done under local anaesthesia. It can be safely done under either Spinal Anaesthesia (half body anaesthesia) or General Anaesthesia (full-body anaesthesia). We will check your heart (ECG), your lungs (Chest X rays) and perform blood tests to ensure your fitness for operation. Rest assured that the safety of our knee replacement patients is our top priority.

4. Deep vein thrombosis (DVT)/ Pulmonary Embolism (PE) (<0.5%): DVT (aka Economical class syndrome) happens when the blood flows out of the lower limb is slow and sluggish, such as prolonged sitting in a very cramped long haul flights or after lower limb surgeries such as total knee replacement.

It will be dangerous if the blood clot is dislodged and clogged up the lungs vessels (Pulmonary Embolism). But rest assured that we have multiple methods to prevent such complications: blood-thinning medication, mechanical foot pumps to promote blood flow.

The best prevention is early walking exercises (the natural way to promote blood flow) after surgery. We have advanced painkilling techniques that allow our patients to walk even on the same afternoon after a total knee replacement surgery.

In conclusion, I'd say that total knee replacement surgery is not a small procedure. Comparatively, it's not as risky as those open heart/ open brain surgeries. If done under experienced hands, the success rate is well above 97-98%.

Almost all of my own patients will be able to walk around independently, pain free within 3 months. I hope this will give you some reassurance if you are exploring about the knee replacement surgery as a treatment option for your knee osteoarthritis.

Read this article to find out everything you need to know about knee replacements in Singapore.

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