Total Knee Replacement (TKR)

Arthritis of the knee is the main indication for a total knee replacement in most cases. It is usually advised for knee arthritis which is causing severe pain and lack of functionality. Normal activities of daily living require a wide range of motion and stability from the knee, a major weight-bearing joint. Arthritis of the knee can affect walking, stair climbing and playing sports. The only other indication is to repair functional stability in cases where the joint or surrounding bone has been destroyed due to severe trauma to the knee.

The decision to do a total knee replacement is only considered once all non-surgical options such as analgesics, anti-inflammatory medications and adjustment of activities of daily living have been tried. Only severe knee pain that affects all activities of daily living warrants a total knee replacement. You, as the patient, will be able to decide if the pain is severe enough for a total knee replacement.

The aim of a total knee replacement

The demands of patients in the 21st century have increased, and many patients participate in the sport into their 7 or 8th decades. Improvement in Total Knee Replacement (TKR) prosthesis designs and materials provide excellent outcomes and enable many patients to return to pain-free activity of daily living.

The knee can be divided into 3 separate compartments: medial compartment, lateral compartment and patella-femoral joint. These 3 separate compartments are interlinked and share the same capsule and synovial fluid. That is why inflammatory arthritis affects all 3 compartments, but chondral lesions or osteoarthritis can only affect 1 of the 3 compartments.

In 25% of patients that require knee replacement surgery, only one of the 3 compartments is involved and the other 2 compartments spared. In those cases, unicompartmental knee replacement will give not only excellent short term results but also better mobility and need smaller revision procedures when the other compartments start to fail. Partial knee replacements seem very inviting, but surgeons must adhere to strict guidelines and prerequisites; otherwise, these procedures will fail early and that in itself defeats the object of partial knee replacement.

Treatment options for knee conditions

There are several different conservative options for treatment of arthritis in the knee, which may include physical adjustments, orthotics and pharmaceutical treatments. Arthroscopic procedures may also be useful to explore before choosing to do a total knee replacement. Arthroscopic surgeries that may be beneficial include:

  • Removal of loose chondral cartilage
  • Meniscectomies
  • Microfracture repair
  • Autograft Chondral implants (OATS/Mosaicplasty)
  • Autologous Chondral cell transplants (MACI/ACI)
  • Synthetic chondral membranes
  • Meniscus allografts and scaffolds

Surgical options for the knee joint

Surgical realignment procedures such as a patellar realignment, elevation and distalisation or a realignment and osteotomy of the tibia and femur may be able to treat various knee conditions. In more severe cases, a total or partial knee replacement may be deemed more suitable.

Approaches to partial knee replacement

In some cases, Dr Morkel may approach the knee for a total knee replacement only to find that a partial knee replacement may be more beneficial. In these cases, he will perform a unicompartmental knee replacement to keep as much of the knee joint intact.

Medial partial knee replacement

This procedure was pioneered in Oxford and with proven excellent long-term results in patients with anteromedial osteoarthritis and no underlying ligamentous instability. The key to the procedure is adherence to the pre-conditions and indications to achieve long-term survival of the implant.

Lateral partial knee replacement

The incidence of osteoarthritis confirmed the lateral compartment is much less patellofemoral or medial compartment osteoarthritis. In this very small selected group of patients, the results with the unicompartmental replacement are also very good.

Patello-Femoral replacement

Replacement of the patella femoral joint has not delivered the same long term results as medial and lateral compartment replacements. In cases where this common condition has rendered the patient impaired, there are a number of prosthetic designs with good medium-term results.

Total Knee replacement designs

Total knee replacements give excellent long term results lasting up to 30 years, but 10% of patients will have discomfort or pain in the knee. Many different approaches in design adjustments of the new prosthesis have tried to address the detail that would guarantee deeper flexion and more natural feeling knee, but at this stage, there is not much to choose from all the different designs. As long as your orthopaedic provides a stable replacement with a full range of motion, you should have an excellent function for activities of daily living and low impact sports and hobbies.

As long as your orthopaedic provides a stable replacement with a full range of motion, you should have an excellent function for activities of daily living and low impact sports and hobbies.

Enhanced recovery after a knee replacement surgery

Soft tissue healing after a partial or total knee replacement is important for the longevity of the prosthesis. It will depend on how much tissue was left intact, but generally, those who undergo partial knee replacements heal quicker. Early mobilisation also plays an important role in the prevention of post-operation complications. The advantage of early mobilisation is that it will lead to less pain and lower risk of deep vein thrombosis. For early mobilisation that is started the same day as the operation, a multidisciplinary approach which involves the anaesthetist, physiotherapists and all the nursing staff, is needed. Lifestyle changes may have to be made after a knee replacement as you may need to avoid high-impact sports, heavy lifting or climbing. You can expect to be back to your normal activities within 4 weeks of surgery. Full recovery may take up to a year.

Complications of a knee replacement

Deep vein thrombosis (DVT)

There is a risk for deep vein thrombosis (DVT) in primary total knee replacements and pulmonary embolism as a complication. Prevention of DVT is important and depends on good hydration, early mobilisation, foot pumps, and chemical trombo-prophylaxis (low molecular heparin, Warfarin and newer anticoagulants).


There is always a risk of infection with major surgeries, and despite advances in prevention and antibiotics, it remains a concern. Prevention is still the best way to cure. For that reason, after a partial or total knee replacement, the patient is investigated for any possible source of infection. Intra-operatively the principles that we adhere to prevent infections is laminar flow operating theatres, prophylactic antibiotics, accurate and precise surgical techniques, prevention of haematomas (collection of blood in operating sites) and special care with barrier nursing. Superficial infections can be treated effectively with antibiotics, but deep chronic infection might need a revision of the prosthesis.

Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS) is a chronic pain condition most often affecting one of the limbs (arms, legs, hands, or feet), usually after an injury, trauma or trauma to that limb. CRPS is believed to be caused by malfunction of the peripheral and central nervous systems. Although rare, it can occur after knee arthroplasty. It is important that it is diagnosed early, and pain modulation treatment is started early for resolution of this potentially debilitating condition. This condition can last for longer than 1 year, and it is the reason why symptoms can still improve up to 2 years after total knee replacement.

Frequently asked questions

Can both knees be replaced simultaneously?

If fit and healthy, patients can safely undergo knee replacements for both knees, simultaneously. The advantage of this would be that you won't need to take more time off from work. You will also only undergo surgery once meaning the anaesthetic and theatre costs will be reduced by half. In some cases, medical aids will have a cap on the prosthesis benefits, and that will preclude bilateral procedures. In elderly patients or patients with underlying medical conditions, there is a higher risk of complications, and thus Dr Morkel will advise that the replacements are done separately.

What will my limitations be after a total knee replacement?

Only a small percentage of patients will be able to do a full squat post knee replacement. After a total knee replacement, you will not be able to participate in high impact sports like jogging, jumping, squash, snowboarding, kiteboarding, wakeboarding and surfing. Patients that are skilled in Alpine skiing, tennis, body boarding and windsurfing will be able to their previous sports as social participants and should only compete at a lower level.

How long after the knee replacement can I drive?

This will depend on Dr Morkel's approach and the condition of the soft tissue, but a general rule is that 4-6 weeks after a total knee replacement should be a safe period to return to driving.

Are minimally invasive procedures a fad or a must have?

Whether or not you will have a scar is not the important part – what is important is that the alignment and tissue tension is at its best to allow for long term outcomes. And while a total knee replacement is a very successful procedure, it still carries a risk for complications which may require follow up surgery. While the cosmetic appearance of the scar is important, it should not be more important than the patient's health or long term outcomes.

What is the best type of knee replacement for me?

It depends on your age, demands and bone morphology. Dr Morkel will be able to choose the most suitable option as he has done a reasonable amount of total knee replacements through his career. He will choose the prosthesis after all the pros and cons have been discussed with you.

What is Computerised Assisted Surgery (CAS), Robotic and Patient Specific Instrumentation (PSI)

There was a time in the evolution of total knee replacements when the correct anatomical alignment of the prosthesis was thought to increase the longevity of the prosthesis. CAS, Robotic-assisted and PSI were developed to improve the alignment of the implanted prosthesis. Both these 2 technologies are available, but improved implant materials (cross-linked high-density polyethene) and instrumentation have made them less crucial for better surgical outcomes. CAS leads to the added cost, longer theatre time and increased risk for complications. PSI can decrease the theatre time, but MRI or CT scans need to be done prior to surgery, which then adds to the cost. There are still very specific indications for this technology in patients with previous implants for femoral or tibial fractures or serious malalignment caused by previous fractures. Unless you want this added, Dr Morkel will only suggest it if necessary.

When is the right time for a total knee replacement?

Once all underlying causes for cartilage wear, inflammatory causes, metabolic (gout), instability and alignment have been treated, and all other non-surgical options have been exhausted, a knee replacement may be suggested. The decision is ultimately up to you as the patient. Whether it will be a total or partial knee replacement will be decided by Dr Morkel once he sees the internal condition of the knee joint.