• First up, what are knee replacements for?

Knee replacement surgery describes a procedure to remove the worn out parts of the knee which was previously causing pain, stiffness, problems walking and even deformities. A knee replacement implant is used to restore the motion and function of the knee, enabling our patients to return to an active lifestyle.  

• Who benefits the most from a knee replacement?

Patients who benefit the most from a knee replacement are those who are medically fit, keep an active lifestyle but are significantly affected by their knee pain, stiffness and loss of function.  These motivated patients will reap the most benefit from their surgery and our rehabilitation program to regain their optimal function and independence. 

• What happens during a knee replacement?

There are several types of knee replacements available; these include partial knee replacements and total knee replacements. Many factors have to be considered before the surgeon decides on the appropriate knee replacement for our patients. There are three compartments to the knee. Partial knee replacements may be considered in younger patients who have developed arthritis in one or two compartments of the knee. A total knee replacement would be advised in older patients with widespread arthritis.

Standard investigations are done before surgery to ensure all our patients are healthy enough to receive anaesthetic medication and undergo the surgery. This is to reduce the risk of medical complications occurring during surgery such as heart attacks and strokes. The anaesthetic doctor will often administer either a general anaesthetic or spinal anaesthetic so that our patients do not experience any pain during the surgery. 

The surgeon will make a vertical skin incision in the middle of the knee. The arthritic and worn out parts of the knee are removed in a measured manner to give the implants a good fit. The metal implants are fixed to the bone using surgical cement. A piece of plastic (polyethylene) is securely placed between the tibia metal plate and femur implant. The patella cartilage is removed and replaced with a plastic patella button. This is to allow the patella to glide smoothly within the knee and prevent anterior knee pain in future. 

Once all the implants have been placed and secured, the knee is washed well with antiseptic and injections are given around the knee to help with pain and prevent infection. The knee joint is then closed with absorbable sutures. To ensure the wound closure is water-tight, we used an adhesive over the wound followed by a water-proof dressing that does not need to be changed for about five to seven days. 

Most of our patients are encouraged to walk within a day or two of surgery. They are also taught how to straighten and bend their knee so that the muscles around the knee do not become tight. Knee swelling may last a month or two and this is normal after knee replacement surgery. We reduce this swelling with anti-inflammatory medication, compression and icing. How much a patient can flex their knee after surgery depends on how much they can flex before surgery. Physiotherapy is crucial as it significantly improves knee movement and flexibility after surgery. 

• The public versus private route for a knee replacement in Singapore

1. 1. Costs
2. 2. Waiting time
3. 3. Expertise
4. 4. Environment
5. 5. Implants choice

• Can you avoid having a knee replacement surgery?

There is very strong evidence for patients to be involved in self-management programs, strengthening and low-impact aerobic exercises.  We also encourage patients with a body mass index (BMI) of more than 25Kg/M² to embark in a weight loss program to reduce their knee pain. Anti-inflammatory medications such as Arcoxia and tramadol (an opiate) are also effective in reducing knee swelling, inflammation and pain. 

Patients often have anterior knee pain while going up or down stairs. This is because of the increased pressure between the patella and the femur. Due to muscle weakness, the patella is also not centered in the knee and grinds against the femur. Patients are rehabilitated with our physiotherapists to perform quadricep muscle strengthening exercises to return the patella to its optimum position in the middle of the knee. 

• What are some signs that you need a knee replacement?

We would advise patients to consider surgery for their knee arthritis if they have persistent knee pain, swelling, stiffness and loss of function despite several months of rehabilitation and  appropriate medication.

Keyhole surgeries to ‘clean up’ arthritic knees have not proven to be effective and not recommended in international guidelines. 

Depending on your age, condition of your knee and physical activities, your surgeon will discuss with you the appropriate type of knee replacement for you. This may be a partial or total knee replacement with or without the use of navigation-assisted or robotic-assisted techniques. 

• What is the best knee replacement procedure in Singapore?  

1. Total knee replacement
2. Partial knee replacement 

Partial knee replacements are suitable for patients whose disease is limited to just one area of the knee. The skin incision is smaller and pain after surgery is lesser than that of a total knee replacement. As such, patients spend a shorter time in hospital and experience a shorter recovery time. Your surgeon will assess your suitability for a partial knee replacement through a clinical examination and MRI scan of your knee.

We do explain to our patients having a partial knee replacement that there is a theoretical risk that other parts of their knee may experience arthritis in the future. If this happens and causes significant pain, we may manage it with medication or convert the partial knee replacement to a full knee replacement. This involves a second operation to remove the previous implants and inserting a full knee replacement implant in the same setting. 

For patients who are about 60 years and above, who have generalised arthritis throughout their knee, we would recommend a full total knee replacement for their symptoms. Through this procedure, all parts of the worn out knee are replaced, including the knee cap. Any ‘knock-knee’ or ‘bow-legged’ deformities can also be straightened with a total knee replacement. 

• How long is the downtime after knee replacement surgery?

Most patients are walking with the help of a walking frame and physiotherapist the day after surgery. This will differ from patient to patient, and is dependent on pain control and symptoms such as nausea. We encourage our patients to walk as soon as they can to prevent their muscles from weakening. We also place the operated knee in a physiotherapy machine to gently straighten and bend the knee in a controlled manner. This is to help stretch out the different muscles around the knee such as the thigh, calf and hamstring muscles. The wound normally takes 2 weeks to fully heal while general swelling may take a month or two to settle. We encourage the use of anti-inflammatory medication and tramadol for pain, as well as ice packs to help reduce knee swelling. 

• Who is suitable for a partial knee replacement?

Partial knee replacements are suitable for patients whose disease is limited to just one area of the knee. The skin incision is smaller and pain after surgery is lesser than that of a total knee replacement. As such, patients spend a shorter time in hospital and experience a shorter recovery time. Your surgeon will assess your suitability for a partial knee replacement through a clinical examination and MRI scan of your knee. 

• What are the advantages of robotic surgery for knee replacements?  

Robotic-assisted knee replacement involves enhanced patient specific pre-operative planning, dynamic joint balancing and robot-assisted bone preparation for accurate implant placement.  

A CT scan of the knee is done before surgery to create a 3-dimensional virtual model of your knee which evaluates your unique bone structure, disease severity and joint alignment. This 3D virtual model is input into the Mako computer software to create a customised surgical plan for you. Your surgeon will determine the optimal implant size, placement and alignment of your implant. During surgery, your surgeon will make the initial skin incision over the knee and prepare it for the robotic arm. During surgery, dynamic assessment of your knee provides the Mako system real time data and allows your surgeon flexibility to make necessary adjustments to your surgical plan. Your surgeon guides the Mako’s robotic arm to remove the arthritic bone and cartilage from the knee. A virtual boundary provides tactile resistance to help the surgeon stay within the boundaries defined in your surgical plan and prevents soft tissue and ligament damage.  Once the bone cut are made according to the final surgical plan, the implants are secured with bone cement. Robot-assisted knee replacements have proven to be more accurate and reproducible than conventional knee replacement surgery. This gives patients a more predictable surgical experience.

• How much improvement can you expect after a knee replacement operation?   

We expect all our patients to experience significant improvement in their function after knee replacement surgery. They will be able to walk on flat grounds, and negotiate stairs once their initial pain is managed and muscle strength returns.  With optimal rehabilitation and muscle strengthening, we expect our patients to perform their daily activities better than before their surgery. This is due to better knee movement and reduced pain compared to before they had their surgery. We have found that patients who undergo a full rehabilitation and physiotherapy program tend to have the most improvement in their physical function. 

• How to get optimal results after your knee replacement

The best way to rehabilitate after surgery is to focus on controlling pain and knee swelling, followed by muscle strengthening and stretching. Your surgeon will prescribe anti-inflammatory and opiate medication after surgery to enable earlier walking and knee stretching exercises. Ice packs are used to reduce swelling of the knee and physiotherapists will be on hand to guide you with the necessary exercises to improve your rehabilitation journey. We would like most of our patients to start walking the day after surgery to prevent muscles from getting weak and the knee joint from getting stiff. The surgical wound will take about 2 weeks to fully heal while the general swelling of the knee may take a month or two depending on patients. 

• What to expect post operation?

Our patients are given patient controlled analgesia (PCA) after surgery to facilitate timely and appropriate treatment for pain. They may press a button in a hand-held device when they are in pain to receive a small dose of painkillers. With the PCA, our patients do not need to wait for a nurse or doctor to dispense the painkillers when they need it. The machine that holds the painkiller has been programmed to ensure only safe doses of the painkiller are given each time to prevent side effects. 

X-rays of your knee are done after surgery to ensure the implants are well placed and the alignment of the knee is optimal. 

Rehabilitation and physiotherapy is a very important part of recovery. Our physiotherapists will help you on your feet and provide guidance as you walk up and down with the use of a walking frame. Once you are walking well and safely, the physiotherapist will allow you the use of a quad-stick or walking stick. Most of our patients are able to walk without any walking aids at about 2 to 3 weeks after surgery. 

We follow up our patients in clinic 2 weeks and 6 weeks after surgery. This is to ensure that their surgical wounds have healed, the knee swelling is improving and the movement of the knee is progressing well. We provide hospitalisation medical leave for our patients as they undergo rehabilitation before returning to work. The duration of the hospitalisation leave will depend on their progress and the type of job they do.