Mako Robotic Partial Knee Replacement

Learn about advanced robotic knee replacement surgery – By Dr Daniel Meyerkort – Perth Orthopaedic & Sports Medicine Centre

Robotic MAKO Partial Knee Replacement / Unicompartmental Knee Replacement

Robotic partial knee replacement replaces the worn compartment, leaving the remaining two thirds of the normal knee intact. It most often replaces the medial compartment of the knee, but can also be used to replace the lateral compartment and patellofemoral joint. The MAKO Surgical Robot is used to allow precise bony cuts and implant positioning.

About Perth Orthopaedic & Sports Medicine Centre (POSM)

Perth Orthopaedic has been providing Elite Orthopaedic care to the community of Western Australia since 1988. It is the longest running and largest Orthopaedic practice in Perth. It has an established reputation for quality and compassionate care. Dr Meyerkort is a specialist surgeon and works at Perth Orthopaedic.

Information on the MAKO Robotic Partial Knee Replacement can be found here, from Stryker

The above link is to Stryker patient medical education with print and video resources about MAKO Robotic Partial Knee Replacement.

Robotic Partial vs. Total Knee Replacement

There are benefits unique to both procedures, and your knee osteoarthritis pattern must be suitable to be considered for a partial knee. For suitable patients, partial knee replacement has the following advantages:

  • Smaller operation with a quicker recovery
  • Shorter hospital stay
  • Preserved kinematics and natural motion of the knee
  • Better range of motion
  • Higher Oxford knee scores (higher is better)
  • Lower risk of surgical complications (infection, thrombosis, stroke and myocardial infarction)

These benefits have been well published by the Oxford University Group from the UK and can be found by clicking on these links to The Bone and Joint Journal and the Lancet.

The advantage of total knee replacement is that it encompasses a lower lifetime risk of re-operation. The risk of re-operation is around twice as high for a partial knee replacement when comparing it to a total knee replacement. There are many reasons for this, which include:

  • Progression of disease (Arthritis progressing in the normal part of the knee)
  • Loosening
  • Ease of conversion

Suitability for MAKO Robotic Partial / Unicompartmental Knee Replacement

Pain should be localised to a single part of the joint, usually the inner aspect, to be suitable for a partial knee. You should be able to localise the pain by pointing with one finger. Pain is often related to activity and may disturb sleep. On physical examination pain is localised to a specific area of the joint and Lachman’s test should demonstrate an intact ACL ligament.

Investigations before Robotic MAKO Partial Knee Replacement

Weight bearing knee XR’s confirm the diagnosis. An MRI scan may be necessary to assess suitability. A CT scan is required for pre operative planning with the MAKO Robot.

Timing your MAKO Robotic Partial Knee Replacement

Only you can decide when the right time is for you to pursue your partial knee replacement. Your knee will never be too worn, nor will you be too old. As a guide many patients consider surgery when:

  • Pain is stopping them from enjoying their normal activities and recreation.
  • Pain is disrupting night sleep.
  • Knee function, as assessed by the Oxford Knee Score, is in the mid 20’s or below.

How long will my partial knee replacement last?

As a guide, a partial knee replacement should provide most patients with 15-20 years of trouble free use before requiring conversion to a total knee replacement. Older patients have a lower chance of conversion. The Australian Joint Registry shows the number of well performing patients by age at 16 years follow up:

  • < 55 – 63%
  • 55 – 64 – 73%
  • 64 – 75 – 81%

MAKO Robotic Partial Knee Replacement surgery – The Patient Journey

High dose antibiotics are given to minimise infection risk and a small incision is used to expose part of the knee joint. A small amount of bone is resected from the distal femur and proximal tibia to accommodate the knee replacement. The artificial joint involves a metal femur and tibia, which is fixed to the bone. An ultra hard wearing polyethylene bearing links these surfaces. Local anaesthetic nerve block and high volume local infiltration are used to make your recovery comfortable. Mobilisation with the physiotherapist commences with full weight bearing and movement of the knee on the day of surgery. Most patients remain in hospital for 1-2 nights. Surgical and anaesthetic techniques have led to a vastly improved patient experience, especially compared to 10-20 years ago. Most patients are happy by 6-weeks however your best functional result can take up to 12 months.

MAKO Robotic surgery / Computer navigation – Partial Knee Replacement

The robotic system is a form of computer navigation with the surgeon performing the bone cutting with a robotic assisted arm. A pre -operative CT scan is matched to intraoperative landmarks (image based computer navigation) and the intended implant position can be assessed  in virtual reality. Changes to the intended bony cuts can be performed in virtual reality before committing to physical cuts. The partial knee is then implanted in the same manner as a conventional technique.

Robotic vs. Computer Navigation vs. Conventional Partial Knee

Both robotics and computer navigation allow for more accurate bony cuts and less ‘outliers’ than conventional techniques. Loosening is related to poor tibial implant position and accounts for 40% of partial knee replacement failures. This number may be reduced with robotics and computer navigation. 60% of partial knees however still fail for other reasons and it would not be anticipated that more accurate enabling technology would solve this issue. In particular, 31% of partial knees fail for progression of disease, which is related to correct patient selection.

Risks of Robotic Partial Knee Replacement

The main risk of partial knee replacements is the future conversion to a total knee replacement. Other risks include:

  • Infection
  • Blood clots
  • Nerve/blood vessel damage
  • Fracture
  • Dislocation/ Instability
  • Bleeding
  • Pain/stiffness

An Overview of Partial Knee Replacement – The American Academy of Orthopaedic Surgeons


Learn about Robotic Total Knee Replacement



Robotic assisted knee replacement is a technology to allow accurate implantation of the prosthesis. Robotic assistance has been shown to be very accurate in performing bone resection compared to conventional ‘jigged’ knee replacement. Other surgical aids such as computer navigation have also been shown to allow for accurate bone cuts when compared to conventional knee replacement. As yet, clear data does not exist to demonstrate that robotic assisted knee surgery leads to better implant survival or a higher level of function. Robotic knee surgery is a semi autonomous system, so the surgeon remains in complete control of your surgery.


The standard inpatient stay after robotic knee replacement is 2 – 4 nights after surgery. Prehabilitation with your physiotherapist is important before surgery as it has been shown patients with strong muscles have a quicker recovery, shorter hospital stay and higher level of function. The MAKO surgical robot has a ‘haptic’ boundary around the cutting tip of the robot. In cadaveric studies this has shown to lead to low levels of soft tissue damage compared to conventional knee replacement. It has been postulated that this may lead to a quicker recovery after surgery, This has not currently been demonstrated in high quality clinical trials.


Robotic partial knee replacement can be a good option for relief of pain and regaining your function if you have isolated (usually medial) compartment arthritis of your knee. Robotic partial knee replacement allows for a short recovery, low levels of pain, high satisfaction and a lower rate of medical complication compared to total knee replacement. The disadvantage of partial knee replacement compared to total knee replacement is there is a higher rate of repeat surgery (conversion to total knee replacement) in the future. In my practice, partial knee replacement is a good option for patients with isolated, medial sided pain. I recommend discussion with your surgeon about the pros and cons of partial vs total knee replacement and your suitability for partial knee replacement.


Many factors are involved in successful partial knee replacement surgery. A list of all partial knee replacement prosthesis can be publicly accessible from the Australian Joint Replacement Registry. You can ask your surgeon about the expected survival of the prosthesis being used. Other factors are important in successful surgery, the most important being patient selection. Patients expected to do well from partial knee replacement surgery have isolated (usually medial) pain, an intact ACL and a good range of motion of the knee. Accurate bony cuts are also important for successful surgery. The MAKO surgical robot is able to assist in performing accurate bone cuts for insertion of your partial knee replacement.


It is best to have the surgery that is best suited to your knee! Benefits of partial knee replacement include low length of stay, faster recovery, lower risk of infection, lower rate of medical risks and a more ‘natural’ feeling knee due to retaining important structures such as the ACL ligament. However, if you are not suitable for partial knee replacement you are at risk of ongoing pain and dissatisfaction if your arthritis is widespread. Benefits of total knee replacement are a lower risk of repeat surgery (conversion to total knee replacement). A good discussion with your surgeon will determine if you are better suited to partial or total knee replacement.


The best performing partial knee replacements in Australia with over 10 years follow up are the Depuy Sigma and the Zimmer Zuk. The respective success rates at 10 years are 94% and 91% respectively. This means that over 9 out of 10 patients are still functioning with their original prosthesis. The most common prosthesis being used currently is the Stryker Restoris, as the is used exclusively with the MAKO surgical robot. As this is a new technology only short term results are available. At 3 years follow up, the Stryker Restoris has a lower failure rate than the Depuy Sigma and Zimmer Zuk.


Robotic partial knee replacement is designed to get you back to your normal active life. You can work (including heavy manual work), walk, golf, cycle, swim, snow ski, play tennis, beach walk, bush walk and stay generally fit and active. Prolonged, high impact sport such as AFL, soccer, hockey and running are probably best avoided as will increase your risk of early implant failure.


This depends on the side of your surgery, whether your car is automatic or manual and how well you recover after surgery. As a general rule, when you can comfortably walk without crutches and are not taking strong (morphine based) pain killers you are safe to drive. This is between 4 – 6 weeks for most patients, but can be sooner.


West Perth & Canning vale