Partial Knee Replacement

Partial Knee Replacement

What is a partial knee replacement?

A partial knee replacement is also known as ‘uni-compartmental knee replacement’.

Uni-compartmental knee replacement surgery is a procedure to replace a single area (aka ‘compartment’) of the knee, when the joint has become very worn through osteoarthritis.

Osteoarthritis can affect the joint surfaces of any part of the knee, and we talk about the knee in terms of its compartments.

The medial (inside) and lateral (outside) compartments are found between the end of thigh bone (femur) and shin bone (tibia). The third compartment lies between the back of the kneecap (patella) and the front surface of the thigh bone (femur).

Typically partial knee replacement is carried out to replace the surfaces of the medial compartment of the knee.

When might I need a partial knee replacement?

If you’ve been suffering for a long time with osteoarthritis symptoms in the medial side of your knee, such as pain, swelling, limping and difficulty performing day to day activities, it may be time to consider surgery. It may be that you’re no longer coping, despite injections and physiotherapy and painkillers.

It’s not uncommon for patients who’ve had a history of a torn knee cartilage or previous arthroscopic (keyhole) knee surgery, to go on to develop arthritis years later.

Who is suitable for a partial knee replacement?

In the past we tended to only consider partial knee replacements for older patients, but increasingly we’re offering it to younger patients.

By no means is everybody suitable for partial knee replacement and in fact, only about 20% of patients who have knee osteoarthritis are suitable. There are a few criteria we use to determine who may be suitable, and who definitely isn’t.

Firstly, the knee must either be straight or can be placed in a good alignment when I assess you. Sometimes knee arthritis creates a very big bend in the knee, which makes it unsuitable for a partial knee replacement.

Secondly, the arthritis must only be in a single compartment, i.e. the medial compartment.

If it’s in more than one compartment, then a total knee replacement is likely to be required.

Thirdly, the ligaments that support the knee must be intact.

Finally, there may be medical conditions such as rheumatoid arthritis, which would be best served by a total knee replacement.

What are the advantages and disadvantages of a partial knee replacement?

A partial knee replacement replaces a single compartment in the knee, and although it’s still a significant surgical procedure, it’s less invasive than a total knee replacement.

This means a quicker recovery and many patients find they can be back to activities such as golf, in around 8-12 weeks. Patients tend to be more satisfied and experience less discomfort than a total knee replacement.

The disadvantage of a partial knee replacement is that in comparison with a total knee replacement, it is more likely to need revising in the future (which means removing the old, partial knee replacement components, and then carrying out a total knee replacement).

This happens in around 8 – 10% of patients who’ve had a partial knee replacement, whereas for total knee replacement patients, the revision rate is approximately 4 – 5%.

What happens during a partial knee replacement?

On the day of the surgery, you will be given a spinal anaesthetic so that your leg is completely numb. You may also be offered a light sedation if needed.

A short incision is made over the medial (inside) side of the knee and a ‘jig’ is used to guide the cutting of the worn ends of the thigh bone and tibia bone, ready to receive the new implant. The implant is made of metal, and it’s fixed in place, usually with cement.

A polyethylene plastic insert is positioned in between the metal surfaces, so they can glide easily upon each other.

The incision is closed with stitches that run under the surface of the skin, so there’s no need for the removal of stitches.  The skin is closed with skin glue, which provides a water-proof barrier and helps reduce wound bleeding.

The partial knee replacements I use have an excellent track record, and I can tailor it to the individual’s needs.

We know from research that if you’ve reached the age of 80, and you only have medial knee compartment arthritis, you’re very unlikely to go on to arthritis elsewhere in the knee.

If you’re a younger patient with medial compartment arthritis, it’s much more likely that you will eventually go on to have arthritis throughout your knee

I often find that my patients who have partial knee replacements, feel that they are more comfortable and that they can readily kneel on the knee. And so, if your occupation or hobbies, require kneeling, this may be a good option for you.

All in all, a partial knee replacement is worth considering if you have knee arthritis which is isolated to the medial compartment.

When you come to clinic, I’ll be taking a through history of your problem and how it’s impacting on your lifestyle. I’ll carry out a thorough medical examination and the necessary imaging such as an MRI scan and X-rays.

If you have questions around partial knee replacement versus a total knee replacement, and whether surgery could help you regain a pain-free active life, don’t hesitate to book an appointment.