Mr RH is a 66-year-old man on the surgical waiting list for a total knee replacement. He suffered a tennis injury at the age of 19, resulting in a prolonged dislocation.

Mr RH had continued to have frequent dislocations of the patella, which he re-aligned. An arthroscopy five years ago provided some pain relief. At present, he reports an average pain of 8/1 O and has significant functional impairment. Pain has a severe effect on his sleep, activities of daily living and hobbies. Mr H can only walk 100 metres and is unable to sit in a car for 30 minutes or more. He takes fosinopril for hypertension, and his analgesic management for his knee consists of 4 x paracetamol 500 mg/codeine phosphate 30 mg daily. A pharmacist reviewed his pain management and suggested that the paracetamol/ codeine be ceased and replaced with regular paracetamol and a trial of 5 mg of sustained-release morphine twice daily.