Total knee replacement: pursuit of the paramount result.

What is the measure of its success? Total knee replacements (TKRs) are increasing throughout the developed world. More than 600 000 primary TKRs were performed in the USA in 2009, with >95% of these done on people with advanced knee OA [1]. The use of TKRs is increasing especially in individuals <65 years of age [1], who have less functional impairment than their older counterparts [2]. Although TKR is generally regarded as a highly successful procedure, emerging evidence suggests that 15–20% of people who have undergone TKR had persistent pain after the usual period of rehabilitation [3]. This means that over 100 000 people who undergo TKR experience suboptimal outcomes every year, which is roughly equal to the annual incidence of RA [4]. These observations highlight the importance of identifying patients at risk of suboptimal outcome and devising interventions to improve outcomes in these at-risk patients. An increasing number of studies have assessed outcomes of TKR, but there is no consensus on whether to define success based on the degree of improvement from pre-operative status (the journey) or based on the level of pain or functional status achieved at a specific point in time (the destination). In this issue, Judge and colleagues report TKR outcomes in a large community-based cohort in the UK, focusing on outcomes assessed at 6 months post-surgery (the destination) [5]. The investigators focus on the pa-tient's acceptable state of symptom, the highest level of symptomatic burden at which the person still feels well [6], arguing that this metric is what matters to the patient and has been shown to be related to satisfaction with surgery. The authors identify several independent preoperative risk factors for achieving poor Oxford knee scores at 6 months post-operatively, including poor preoperative functional status, greater anxiety and lower socioeconomic status. Although pain and functional status post-TKR are highly correlated, they may carry different predictors. In fact, authors report that age and gender were predictive of post-operative functional status, whereas preoperative depression and functional status scores were associated with pain at 6 months. The study confirmed the finding observed in several previous studies that preoperative functional status seems to be one of the strongest predictors of post-operative functional status [7, 8]. In contrast to other reports [9], the authors did not find an association between BMI and post-operative pain or function. Although the overall rate of follow-up was modest (55%), it was even …