Unicompartmental Arthritis

Osteoarthritis of the knee is where the articular cartilage on the surfaces of the bones in the joint wears away to expose bare bone. The bare bone rubbing on bare bone in the joint can cause the following symptoms:-

  • pain (which tends to be a deep, achy, nauseating pain that often radiates down the shin and which tends to be worse towards the end of the day or after exercise)
  • swelling (which is partly due to the build up of bone spurs around the joint (osteophytes) and partly due to a build up of excess joint fluid (an effusion)
  • stiffness (partly due to osteophytes, but largely due to thickening up of the joint capsule and tightening of the ligaments and tendons)
  • deformity (if the bone begins to wear away then the joint can become angled, with varus (bow legged) or valgus (knock knees) deformity
  • disability (the above symptoms end up restricting a patient’s function, and once someone loses their cardiovascular fitness and strength, then often everything tends to go downhill)

Arthritis can affect the whole knee joint, but sometimes it affects only part of the joint. The most commonly affected ‘compartment’ of the knee is the medial (inner) side of the joint. The second most commonly affected part of the knee is the patellofemoral joint. The least common place to have unicompartmental arthritis in the knee is the lateral compartment (the outer side) although this does occur not infrequently.

When there is arthritis in a knee, in association with this there are often a number of other concomitant issues, which can include:-

  • loose bits of cartilage, causing intermittent locking
  • unstable flaps of cartilage, that can cause clicking and catching
  • degenerative meniscal tears
  • cartilage debris in the joint, which irritates the lining of the joint, which becomes inflamed (synovitis)

In patients with early to moderate arthritis, a knee arthroscopy (keyhole surgery), with washing out of the joint, tidying up of any rough or unstable areas of articular cartilage, and trimming smooth of any meniscal tears, can help greatly. It will not reverse or ‘cure’ the underlying arthritis, but it can significantly reduce patients’ pain, improve their function, keep their knees going for longer and delay the time when they might end up needing further bigger surgery, with a knee replacement.


CLICK HERE to read about the latest research on knee arthroscopy for arthritis


The great advantage of knee arthroscopy for early to moderate arthritis is that it is much easier and lower risk than knee replacement surgery, with a much much faster recovery. Joint replacements are really designed for older patients – the younger a patient is when they have a knee replacement, the more they will use the joint and the greater the rate of wear and tear will be. Also, younger people live longer. Therefore, the younger a patient is when they have their joint replacement, the more likely it is that the artificial joint will fail within their lifetime and need replacing again, with a revision joint replacement (which is an even bigger, more risky operation, with slower recovery, lower patient reported outcome scores and lower functional scores, and which also tend not to last as long as a primary joint replacement). Therefore, anything that can reasonably and effectively delay the need for actual artificial joint replacement surgery is a good thing – and that most definitely includes knee arthroscopy.


CLICK HERE for more information about Knee Arthroscopy


Realignment Osteotomy

If there is a significant varus deformity in the knee (with medial  arthritis) or valgus deformity (with lateral arthritis), then the knee joint can be straightened up with an operation called a realignment osteotomy. This involves cutting the bone of either the tibia (for medial disease) or the femur (for lateral disease), opening up a wedge to straighten the leg, and the fixing the bone in the new straight position using a metal plate and screws that are inserted onto the bone.

Realignment osteotomy offloads the damaged side of the knee, putting more of the patient’s weight over onto the normal undamaged side, thereby reducing the patient’s pain. It does not ‘cure’ whatever arthritis is in the joint but it does improve patients’ symptoms and keep them going for longer, delaying the subsequent need for joint replacement surgery.


Partial Knee Replacement

Total knee replacement is a highly effective and extremely successful operation. Patient satisfaction is about 90%, and 95% of knee replacements are still in and working after 10 years's use. However, it is a big operation and it takes several months to actually get over the surgery.

For patients with arthritis in just one part of the knee can potentially have just the damaged part of the knee replaced rather than having the whole joint done. Partial knee replacement is a smaller operation with faster recovery. Less bone has to be removed (which is better for any potential future revision surgery that might need to be performed). Also, with total knee replacement, the anterior cruciate ligament is always removed and the posterior cruciate ligament may sometimes be removed as well. With partial knee replacement, both the anterior and posterior cruciate ligaments are left alone, as are the other undamaged parts of the knee. Therefore, partial knee replacements feel more like a normal knee than total knee replacements do, and partial knee replacements have better patient reported outcomes and functional outcomes.

The very latest and best option now available for partial knee replacement surgery is the ConforMIS custom-made i-Uni prosthesis. A CT scan of the knee is taken and custom-made cutting blocks and prostheses are made that exactly match the precise size, shape and contours of the patient's knee. This means that the prostheses perfectly fits your knee, instead of the bone of your knee needing to be cut away to match the size and shape of a standard off-the-shelf prosthesis. Therefore, even less bone needs to be removed, and the custom-made knees feel even more like the patient's own normal knee.

Mr McDermott was the first surgeon in the UK to implant a ConforMIS G2 lateral i-Uni prosthesis - CLICK HERE for more info

CLICK HERE for more information about the ConforMIS custom-made i-Uni knee