However, a significant percentage (up to 20%) of patients report dissatisfaction after knee replacement. Careful patient selection and pre-operative optimisation are critical to achieving the best outcome. Proceeding directly to knee replacement is often the wrong thing to do – a better outcome may be achieved initially with a targeted rehabilitation program.
Severity of Osteoarthritis on X-ray is key.
Multiple studies have shown that patients undergoing total knee replacement for a mild grade of osteoarthritis have a poorer outcome. This may because their expectations were too high, or that there are other, non-structural, causes for the patient's symptoms. Joint dysfunction due to muscle weakness or neuropathic pain may worsen after major surgery such as knee replacement.
Patients with a Kellergen-Lawrence grade <2 (ie no 'bone on 'bone' arthritis – Figures 1 and 2) should always undergo a targeted rehabilitation program before considering surgery. Strategies such as exercise, NSAIDs, and weight loss offer proven and sustainable benefits for symptom control. Regular high cadence, low resistance cycling is particularly effective. Additionally, studies in obese patients suggest weight loss through a combination of diet and exercise can lead to a 50% reduction in arthritic knee pain.
Injection therapy is also an option in patients with refractory symptoms but only mild radiographic change. Corticosteroid injections provide on average 2-3 months of relief, although multiple injections have negative effects on cartilage. Visco-supplementation injections and platelet rich plasma (PRP) injections do not have this effect, and may provide longer term relief. Despite their cost (approx $500) many patients may prefer a single injection than regular NSAID use.
The Value of Preoperative Exercise and Optimisation
Even in patients with severe arthritis, preoperative exercise prior to knee replacement can improve outcomes. In a 2017 meta-analysis, Moyer et al combined the results of 35 studies including almost 3,000 patients, and found ‘prehabilitation’ led to significant improvements in pain, function, and length of stay.
Weight loss can also decrease the risk of major complications following surgery. A body mass index (BMI) >40 is associated with an increased risk of deep infection, wound drainage, and cardiovascular complications following knee replacement. Studies show patients who lose >5% body weight pre-operatively will significantly lower their perioperative risk.
Whatever the grade of arthritis, management should be targeted to each individual patient. The Axis Osteoarthritis Clinic involves a multi-disciplinary approach including Sport and Exercise Physicians, Orthopaedic surgeons, a dietician and clinical exercise physiologist. In this way we hope to be able to deliver high-quality care for patients with a range of joint symptoms.