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have an underestimated effect on outcome. Mancuso et al70 assessed the expectations of 405 patients before and after THR.70 Only 174 (43%) reported their expectations as being fulfilled ‘completely’, and 130 (32%) felt their expectations were only ‘somewhat’ fulfilled. They found that patients with a fulfilled higher level of expectation included those of younger age, with active 438 M. S. SRIDHAR, C. D. JARRETT, J. W. XEROGEANES, S. A. LABIB THE JOURNAL OF BONE AND JOINT SURGERY employment, who had no complications and no post-operative limp, who had better pre- and post-operative Lower Limb Core scores,71 and with a BMI < 35. The overweight patient who cites their knee pain as a barrier to exercise and the reason they cannot lose weight in order to meet the orthopaedic surgeon’s criteria for surgery often presents a dilemma. These patients often say that they will lose weight with a painless, well-functioning prosthetic knee joint. Improvements in function and quality of life occur within three months of TKR so the perceived obstacle to weight loss should be lifted by this time.72-75 A prospective, continuous study of 529 patients who underwent primary TKR was recently reported by Dowsey et al.76 They aimed to investigate weight change and the functional and clinical outcome in non-obese and obese groups 12 months post-operatively. After 12 months, 40 (12.6%) of the obese patients had achieved a clinically significant weight loss of 5%, but 107 (21%) had actually gained weight. The change in weight was less in the obese and morbidly obese patients than in the non-obese. Adverse events occurred in 30 (14.2%) of the non-obese, 59 (22.6%) of the obese, and 20 (35.1%) of the morbidly obese patients. The authors showed that for each unit increase in BMI the risk of incurring an adverse event increased by 8%, even after adjustment for age and gender. Most noteworthy were the increased rates of peri-prosthetic infection and symptomatic deep venous thrombosis in their obese patients. Several studies have shown an increased risk of infection in obese patients. Namba et al77 showed that the risk of infection was 6.7 times higher in obese patients undergoing TKR. Operative and tourniquet times have not been shown to be longer in obese patients undergoing TKR.78,79 The subcutaneous fat layer is poorly vascularised and is abundant in obese patients, and it has been suggested that the greater extent of surgical dissection often required can lead to haematoma and/or seroma formation and prolonged drainage.
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