Knee ‘osteoarthritis’ is a term for ‘wear and tear’ in the knee. This osteoarthritis is caused when the lining of the knee (articular cartilage) becomes thinner, fragments and wears away. You will be at a higher risk of developing arthritis if you have had a previous injury to your knee, particularly if you have injured ligaments, menisci or articular cartilage in the past.
Symptoms and signs
This classically causes a gradual decline in the function of your knee. Pain and stiffness are key features. You may notice over a long period of time your knee has periods where it improves and then worsens. Sadly the arthritic process will progress so your bad weeks come around too frequently and the good days disappear. The time scale this occurs can vary from person to person secondary to many variables and so is difficult to answer the frequently asked question – ‘When will I need a knee replacement?’
Non operative treatment
Initially all treatment should be focussed on educating the patient of their diagnosis and the likely path their knee will walk in the future! Symptom control is key and this can vary on an individual level from anti-inflammatories or painkillers / acupuncture / physiotherapy / weight loss / braces or sticks / steroid injections and viscosupplementation injections.
Partial Knee Replacement
As seen in the ‘basics’ section of the website the knee essentially consists of three joints. The kneecap joint (patellofemoral joint) and the joints between your thigh bone and shin bone on the inside and outside of the knee (the medial and lateral tibiofemoral joints). It makes sense therefore in certain patterns of wear that we replace only the part of the knee that is worn.
The knee must meet strict criteria to qualify for this – namely the knee must have good movement, not be too bent or deformed and have intact ligaments. The medial knee compartment is replaced far more that the lateral knee compartment or knee cap joint.
The partial knee versus total knee debate
Doing a knee replacement is a compromise. It is the best solution engineers and surgeons can provide to mimic the anatomy and function of the knee. Certainly there are positives and negatives when comparing a partial knee replacement to a total knee replacement.
Positives to partial knee replacement
Smaller ‘minimally invasive’ incision, lower levels of post operative pain, lower chance of needing a blood transfusion, lower infection rate, feels more like a normal knee as ligaments are preserved, earlier recovery, more movement, can be revised relatively easily to a total knee replacement if needed.
Negatives to partial knee replacement
The rest of the knee may wear over time and thus need replacing and a partial knee replacement has higher revision rates than total knee replacements (revision rate – the rate of needing to remove the implants and replace with another total knee replacement). I think that historically the revision rates were higher because of implant design / technique / low numbers performed and certainly when people had ‘pain’ after a partial knee they were revised to a total knee quickly… sadly many of the ‘painful’ partial knees continued to have a ‘painful’ total knee replacement. Surgeons have learned that revising implants for ‘pain’ with no cause found tends to lead to more misery for the patient and the surgeon. Another reason they are revised sooner is because they are put in physiologically younger, more active patients who get on and use them!
How long will my knee replacement last?
We know from research that the younger the patient has a joint replacement the higher the chance of it needing revising. If you have a total knee replacement under the age of 55 then you have a 12% revision rate at 10 years compared to a 2% revision rate if you are over the age of 80 (clearly very significant thus patients will need to be aware and counselled about the likelihood of needing another knee replacement in the future). Pooled national data suggests that the failure rate for a partial knee replacement is 5% at 5 year and for a total knee is 2% at 5 years.
Total Knee Replacement
This is the historical ‘gold standard’ of treatment for the knee with severe arthritis. Ideally a multitude of methods to try and control your symptoms should have been exhausted before you commit to having a total knee replacement. This is major surgery where the lining of your knee is removed and replaced with metal both on the end of your tibia and femur. In between the metal you have a plastic insert that acts like the lining of your joint.
In certain circumstances the lining of your patella may be removed and replaced with a plastic ‘button’. This is a very effective method of reducing pain from arthritic knees. The procedure will take several weeks to get over the acute surgery and you will ‘settle in’ to your new knee rapidly and continue to improve over the course of 18 months. Evidence would suggest that more than 80% of patients are happy with a knee replacement. My feeling is that in my practice and in discussion with knee colleagues that this figure is anecdotally higher.
Osteotomy is the process of cutting bone and realigning the knee by pivoting on this cut area. This may be performed typically for the younger, active patient with arthritis or someone with chronic ligament damage. Scans and X-rays of the whole of your leg need to be taken to work out the way your weight goes through your knee. Using computer software we can work out how much we need to alter the shape of your bone. It involves changing the way that your weight is transmitted through your knee – essentially off-loading the painful part of your knee. This involves a cut to your tibia and/ or femur (depending on your wear and tear pattern and severity) changing the shape of your bone and fixing it in a new place to heal with a plate and screws. A bone graft may need to be taken to fill in the gap left in the bone. The most common type of osteotomy is for people who have arthritis mainly affecting the medial part of the knee – people who notice they are becoming more ‘bow-legged’. There are strict criteria to follow to ensure a good outcome. Poor outcomes can be seen in the older, smoker with more advanced arthritis.