Partial knee replacement (medial compartment)

This article describes a new treatment option for patients with degenerative knee joint diseases such as osteoarthritis: partial knee replacement. This will be of help to those patients who are looking for an alternative to a total knee replacement in order to, for example, have a shorter rehabilitation period.



Partial knee replacement is a viable surgical treatment option in some patients with isolated degenerative joint disease, when wear is confined to a particular area of the knee and the remainder of the articular cartilage is in good condition. Surgical treatment for degenerative conditions of the knee can include arthroscopic knee surgery (keyhole surgery), osteotomy (cut is made in bone to improve alignment), partial and total knee replacement.

There are several types of partial knee replacement surgery including medial (resurfacing of the inner medial weight-bearing area of the knee), patellofemoral (behind the kneecap) and lateral joint replacement (outer lateral weight bearing area of the knee). The most common type of partial knee replacement surgery is medial unicompartmental resurfacing. This is where the worn surface is prepared and a metal implant is placed on either side of the medial joint with a polyethylene bearing in between.

The aims of surgery are to relieve pain and improve function with long term survival of the prosthesis.

Usual symptoms

Medial compartment osteoarthritis often develops gradually and causes pain over the anteromedial aspect of the knee on weight bearing and exercise. Walking distance is often reduced with difficulty climbing or descending stairs.

X-rays will show narrowing of the joint space on the medial (inner weight bearing area) side due to thinning of articular cartilage (which normally covers the bone in joints).

What are the benefits of partial knee replacement over total knee replacement?

The main benefit of partial knee replacement is that it involves less invasive surgery with a smaller incision which results in less time in hospital and a quicker progression to functional walking. However, it still takes a minimum of six weeks for early soft tissue healing and resolving of surgical incision pain.

What type of medial replacement do you use?

I use the Oxford medial knee replacement which has excellent long term survival rates in the literature. The anterior cruciate ligament (ACL) is preserved which is a further advantage of partial knee replacement (allows a more physiological mechanical result).

Is everyone suitable for medial knee replacement?

No. Patients with early wear and tear of the medial aspect of the knee and an intact ACL are suitable. Patients with very advanced wear may not be suitable and may need total knee replacement.

Is there an age limit to this type of surgery?

No. Patients in their early 40s to 80 year olds may be suitable.

When can I start walking after surgery?

The day after surgery you will get up and fully weight bear with the physiotherapist. Most patients stay in hospital between three and five days.

Surgical approach

The surgical approach is a medial approach approximately 10cm long on the medial edge of your kneecap. Dissolvable suture or clips are used to close the wound and a dressing stays on the knee for two weeks.

The risks of having treatment

There are small risks with all types of surgery. A regional or general anaesthetic would be required and the small risk of wound inflammation or infection is 1% or less. You would also be given an injection or tablet to reduce the small risk of deep vein thrombosis.

Post-treatment follow up

Clinical review is necessary at two weeks to remove dressings and assess early function of the knee. Further reviews are organised at six weeks, four months and at one year after surgery. Physiotherapy would be beneficial for the first two months.

For further information on the author of this article, Consultant Orthopaedic Surgeon, Mr Charles Gibbons, please click here.
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