The saw-wielding robot that can make new knee joints fit better

More than 90,000 Britons a year have their knee joints replaced. Pascal Murphy, 70, a property maintenance worker, from Edgware, Middlesex, was the first patient in Europe to undergo the surgery where a robot wielded the saw, as he tells ADRIAN MONTI. 


My left knee first began causing me trouble in my early 20s after years of playing football. I had pain and discomfort, particularly when I ran.

I put up with it at first, but after about a year it was aching constantly, so I went to my GP who said the cartilage was damaged, causing inflammation and pain.

He referred me to hospital where they trimmed the damaged cartilage. This seemed to help and I could move more freely again, although I never went back to playing football as I didn’t want to risk knee injuries. I kept fit by playing squash and taking long country walks instead.

More than 90,000 Britons a year have their knee joints replaced, and now saw-wielding robots are able to do the operations

That was 50 years ago — then last year, the ache in my left knee returned. I presumed my job in property maintenance made it worse, as it puts lots of strain on my knees as I’m always climbing ladders, lifting and bending.

By last autumn I was having trouble walking and I couldn’t straighten my left leg. My GP said it sounded like osteoarthritis, meaning the cartilage in my left knee had worn away and bone was now grinding on bone — which is why it hurt.

What are the risks?

As with any surgery, there is a potential risk of infection and blood loss.

‘The Navio System is the next generation of technology and has real promise,’ says Dinesh Nathwani, a consultant orthopaedic surgeon at The London Clinic and Charing Cross NHS Hospital. 

‘It’s very accurate and that has been proven in published papers; but we are yet to see whether it improves knee function long term, too.

‘Currently only 1 per cent of surgeons use technology like this in knee surgery. Hopefully this will encourage more to embrace these methods.’

He referred me to hospital, but the earliest NHS appointment was six months away and I didn’t want to wait — getting around the house was becoming very difficult and I feared falling over, particularly as I live alone.

I decided to go privately and saw a specialist in January.

Both my knees were X-rayed and the specialist said I had severe osteoarthritis in my left one and needed a replacement. I wanted to walk again without pain, so was happy to go ahead.

After the appointment, I got a call from the surgeon’s secretary to ask if I would be happy to have the operation done using a new technique with a robot to cut the bone instead of the surgeon doing it with a saw. The robot follows a precise map to cut away only unhealthy bone and avoids human error.

And because the replacement joint is put in position using special software which takes detailed images of the joint, it should be a better fit and more comfortable.

I had a few days to think about it, but as it sounded well-tested I went ahead. I had the 90-minute operation in late January under general anaesthetic. I woke up with a dressing around my knee and took strong painkillers which numbed any pain.

The next morning I walked along the hospital corridor and began physiotherapy sessions — I could feel my knee becoming stronger every day.

I went home after four days and stayed with my brother for two weeks while my knee recovered. I eased myself off painkillers and discarded the crutch after three weeks — now I take it with me only for extra support on long walks.

I go for a three-mile walk every day to exercise my knee and feel I’ve been given a new lease of life at 70. I even plan to go back to work later this month.


Richard CARRINGTON is a consultant orthopaedic surgeon at the Spire Bushey Hospital in Herts, and the Royal National Orthopaedic Hospital in Stanmore.

A major reason for having a knee replacement is osteo-arthritis, where the cushioning cartilage between the lower end of the thigh bone (femur) and the upper end of the shin bone (tibia) wear completely away and so the bone surfaces rub against one another, causing pain, stiffness and discomfort.

The only way to fix this is with replacement surgery, in which the damaged ends of the bone are cut away with a saw and then covered with metal. A plastic disc is inserted between the bones to replace the lost cartilage.

The entire joint can be replaced (a total knee replacement operation) or just one part of the joint (a partial replacement).

Both procedures take about 90 minutes and patients usually stay in hospital for five nights to start the recovery process.

For several years, robots have been used to help surgeons with orthopaedic operations. The latest technology — called the Navio System — is a revolution for surgeons because it has special software which allows greater accuracy and less chance of removing healthy bone from a patient’s knee.

A hand-held robotic cutter controlled by the surgeon is used to cut away the bone so the artificial replacement joint aligns much better than was ever possible by human judgment.

A hand-held robotic cutter controlled by the surgeon is used to cut away the bone so the artificial replacement joint aligns much better than was ever possible by human judgment

A hand-held robotic cutter controlled by the surgeon is used to cut away the bone so the artificial replacement joint aligns much better than was ever possible by human judgment

The main advantage is that whereas with standard knee replacement operations — even with robots — we need to take scans before and after surgery to know if enough tissue was removed and it was successful, this software gives us a ‘live’ 3D map of the area which we use as a guide. On the screen, the surgeon sees the area turn red if they are in danger of removing healthy bone.

As it’s so new, we don’t yet have much research on its long-term success, but reports from patients who have had knee replacements with this machine are showing good outcomes.

The map also tells us how to align the joint more precisely so it allows the optimum movement for the patient. It even tells us what size implants to use which avoids potential discomfort when they start walking.

To perform the robot replacement, we start off similarly to traditional knee replacement surgery with a 10cm incision made from just above the knee, and the kneecap is moved to expose the ends of the thigh and shin bones.

A probe is then placed over the exposed joint which collects data and relays it back to a computer screen which then displays a 3D map of the knee.

The map highlights the damaged tissue bone on screen and we use that to guide the robot, which looks like an electric screwdriver, to remove damaged bone.

We then use the map to select an implant and fit it perfectly — the software works out how the knee will bend and flex with any given implant so it gives us live feedback on which to choose and what angle to place it at.

We then do our final checks and close the incision.

Patients start walking on the knee the next morning using crutches and start physio-therapy sessions to regain strength and flexibility.

Once they can tackle stairs, they are allowed home. With good rehab, they can be walking more freely slightly quicker — by a few days or a week — than traditional knee surgery.

This system costs around £300,000 so isn’t widely available on the NHS, with only three other London hospitals including the Central Middlesex NHS Hospital at the moment using it. But I am training surgeons in how to use it, so this could change.

It is a major step in how we carry out knee replacements

The operation costs £14,000.