David is a 70-year-old retired accountant who presents to your general practice with severe right knee pain and difficulty mobilising seven days after having a right total knee replacement for osteoarthritis. He has been a patient at your practice for the past four years and his past medical history comprises depression, type 2 diabetes and hypertension, each of which is well controlled with a single first-line agent. He is overweight. Before having this operation he was requiring escalating doses of paracetamol and NSAIDS.

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