CORI® robotic knee replacement

When a knee replacement is needed

Osteoarthritis slowly wears away the cartilage of the knee. Early on, exercise, weight loss, physiotherapy, medication and injections help. When these are no longer enough and pain stops you from walking, climbing stairs or sleeping, a knee replacement enters the conversation.

The decision does not rest on the X-ray alone. It rests on how you live with your knee.

What we try before surgery

Knee osteoarthritis moves slowly, and treatment without surgery helps for a long time:

• Strengthening the quadriceps and low-impact exercise such as cycling and swimming.
• Weight loss. In the knee, every kilo counts several times over with each step.
• Physiotherapy and, where it fits, an unloading brace.
• Painkillers and anti-inflammatory medication for flare-ups, under medical guidance.
• Injection treatments, such as hyaluronic acid or PRP, in early and moderate wear.

When the X-ray shows advanced wear and pain keeps you from living the way you want, a knee replacement becomes the most reliable option.

What CORI® is

CORI® by Smith+Nephew is a robotic assistance system for knee replacement. The surgeon holds a smart handheld tool that works together with a camera and a computer.

• Mapping: the anatomy and movement of the knee are recorded in the operating room, with no CT scan needed beforehand.
• Planning: implant position, leg alignment and ligament balance are set before any bone is cut.
• Execution: the tool removes bone only where the plan says so.

Why alignment and balance matter

An artificial knee has to do two things well. It has to spread the load evenly, and it has to move with the ligaments at the right tension, neither tight nor loose.

If the implant sits slightly off, the knee can feel stiff or unsteady and the materials can wear unevenly. This is where robotic assistance helps: the surgeon sees in numbers how the knee behaves through its whole range of movement, before any bone is cut, and fits the plan to your own anatomy.

Who operates, the surgeon or the robot?

The surgeon. CORI® does not move by itself and makes no decisions. It is a precision tool in the surgeon’s hands. Experience, clinical judgement and choosing the right patient remain the most important part.

Robotic or conventional: what the data show

Studies agree on one point: with robotic assistance, implant position lands closer to the surgeon’s target more consistently, with fewer outliers. Some studies show less pain in the early period too.

What has not yet been proven is that patients have better function or a longer-lasting implant many years later. The data are still coming in.

Conventional knee replacement remains an excellent operation. Robotics is a tool that adds accuracy. It does not replace experience.

Total or partial knee replacement

When wear affects the whole knee, a total replacement is done. When it is limited to one compartment and the ligaments are intact, a partial (unicompartmental) replacement may be discussed. Which one suits you becomes clear from the examination and the X-rays.

Getting ready for the operation

• Pre-operative check-up. Blood tests, a heart assessment and a visit to the anaesthetist.
• Your medication. Some drugs need adjusting before surgery. Do not stop anything by yourself.
• Strong muscles. The stronger the quadriceps before surgery, the easier the rehabilitation.
• Infections. Teeth, urinary tract and skin must be free of infection.
• Your home. Prepare a space without obstacles and think about who will help you in the first days.

The day of surgery

The operation takes place at Metropolitan General, usually under spinal anaesthesia with light sedation, and lasts about one to two hours. First, small markers are fixed to the bone so that the system’s camera can follow the knee. Mapping, planning and bone preparation with the robotic tool come next.

Before the final parts go in, the surgeon checks with trial components that the knee moves well and is stable. The hospital stay is usually a few days.

Pain after surgery and how it is controlled

A knee hurts more than a hip in the first weeks. It is good to know this in advance, because recovery asks for work from you.

Pain is managed with a combination of medicines that act in different ways, with ice and with the leg raised. The target is not zero, but a level of pain that lets you do your exercises. Swelling and warmth in the knee can last a few months, and discomfort at night is common at first. All of this settles gradually.

Recovery, step by step

You usually start moving on the same day or the next, with the physiotherapist.

• First 2 weeks: walking with aids and daily bending and straightening exercises.
• Weeks 2 to 6: the knee bends more easily and stairs feel better.
• Weeks 6 to 12: most everyday activities return.
• Up to 12 months: swelling settles and strength keeps improving.

A knee asks for patience and steady work on the exercises. Timing differs from person to person.

Life with the new knee

• Exercise. Walking, swimming, cycling and gym work are usually welcome. Running and jumping are worth discussing first.
• Kneeling. It does not harm the implant, but many people find it uncomfortable. A soft cushion helps.
• Sensation. A small numb patch of skin next to the scar is common and does not affect function.
• Follow-up. Regular check-ups with an X-ray continue even when everything is going well.

When to call straight away

Most aches after surgery are expected. Some signs, though, should not wait for the next appointment:

• Pain, swelling or warmth in the calf that was not there before.
• Chest pain or shortness of breath. In that case call 166 (or 112) at once.
• Fever, or a wound that turns red, feels hot or leaks fluid.
• A knee that suddenly swells a lot, hurts badly or no longer bends as it did.

If you are not sure, call. One phone call too many bothers nobody.

The risks, honestly

Infection, blood clots, stiffness and ongoing pain are the main risks of a knee replacement. Robotic assistance aims at accurate implant placement. It does not remove the risks and it does not suit every case. We talk all of this through before you decide.

Myths and facts

• Myth: “The robot operates by itself.” Fact: The surgeon holds the tool and performs every step.
• Myth: “With a robot there are no complications.” Fact: The risks of any knee replacement remain.
• Myth: “Robotic means a smaller cut and no pain.” Fact: It means more accurate placement. Recovery always takes time and exercises.
• Myth: “The new knee will not bend.” Fact: With steady physiotherapy, most people bend enough for every daily activity.

What to ask your surgeon

• Is my knee suitable for robotic assistance?
• Do I need a total or a partial replacement?
• Are you certified on the system you use?
• What happens if the system has a technical problem during surgery?
• When does physiotherapy start and how long will it last?
• What are my own risks, given my health?

Common questions