Similar to hip replacement surgery, a knee replacement is indicated when you have advanced osteoarthritis of the knee joint and non-operative measures (eg. Weight loss, anti-inflamatories , physiotherapy etc) are no longer controlling your pain.
Modern day knee replacements are a successful way to treat end stage arthritic knee pain and immobility. It is never really too late to replace the knee so, if you can manage with your current arthritic knee, keep going until such time as it becomes too uncomfortable and is interfering with your quality of life.
Types of Replacement
Arthritic knees that require surgery usually require a Total Knee Replacement. A unicompartmental or “half knee” replacement is reserved for a select few patients who have knee arthritis isolated to one area of the knee joint and who satisfy other preoperative criteria. The revision rate of a unicompartmental knee replacement is significantly higher that a total knee replacement (16% vs 6% at 11 yrs) and therefore there are strict requirements in patient selection.
The 2012 Australian National Joint Registry shows that successful knee replacements have an average of 6% revision rate at 11 years following surgery and that if you are over the age of 65 your revision rate is less than 5% and over the age of 75 your revision rate is less than 3%. Younger patients have higher rates of revision.
A total knee replacement is designed to resurface the femur, tibia and patella and in-between the femur and tibia is a layer of polyethelene. The polyethelene (plastic shock absorber) is the bearing surface which ALL knee replacements use. Unlike in hip replacement surgery there is no ceramic on ceramic knee replacement bearing. There is also no metal on metal bearing so the problem that happened with some metal on metal hip replacements does not exist in knee replacements.
It is anticipated (laboratory studies) that a well aligned and functioning knee replacement should last around 25-30 years before the plastic wears out.
You may have heard about computer navigation , patient specific instruments etc. These are simply tools that some surgeons use to align the replacement during surgery. There are no scientific studies that have proven that a standard surgical technique using instrumentation is any better than computer navigation or patient matched blocks provided the surgeon doing the surgery is a competent surgeon who aligns the implants correctly and balances the knee joint appropriately.
In other words choose a surgeon who is skilled at would he does using any method and you should have a good long term outcome.
Cement or no cement
Knee replacements may either be cemented onto the bone or used in an uncemented fashion where the bone grows onto the prosthesis. There is no scientific evidence that one method is better than the other. My preference has always been to use cement, as patients tend to recover a little quicker in terms of pain and comfort.
The Final word
Surgery is indicated when non-operative measures no longer control the pain and your quality of life is significantly affected. Over 85% of knee replacements will achieve a good pain free functional result however there are some patients (around 5%) that may still have a niggling ache in the replaced knee joint.
Patients are able to play sport including golf, ski, tennis, bowls, cycle, swimming, however, a knee replacement is not designed for impact sports such as running, contact sports, basketball, squash and any sport that results in constant and significant impact on the knee.
We tend to ignore our knees until something happens to them that causes pain. If we take good care of our knees now, before there is a problem, we can really help ourselves. In addition, if some problems with the knees develop, an exercise program can be extremely beneficial. To understand the functions, conditions, surgeries & procedures of the knee better, we have included an interactive animated presentation.
Total Knee Replacement (TKR)
A total knee replacement (TKR) or total knee arthroplasty is a surgery that resurfaces an arthritic knee joint with an artificial metal or plastic replacement parts called the ‘prostheses'
Uni Condylar Knee Replacement
This simply means that only a part of the knee joint is replaced through a smaller incision than would normally be used for a total knee replacement. The knee joint is made up of 3 compartments, the patellofemoral and medial and lateral compartments between the femur and tibia (i.e. the long bones of the leg). Often only one of these compartments wears out, usually the medial one. If you have symptoms and X-ray findings suggestive of this then you may be suitable for this procedure
Revision Knee Replacement
This means that part or all of your previous knee replacement needs to be revised. This operation varies from very minor adjustments to massive operations replacing significant amounts of bone and hence is difficult to describe in full.