The effect of preoperative symptom severity on functional outcome of total knee replacement--patients with the lowest preoperative scores achieve the lowest marks.

To determine if the functional outcome of total knee replacement (TKR) was affected by the level of preoperative symptom severity, the association between preoperative Oxford Knee Scores (OKS), and 2 year OKS, American Knee Society clinical and function scores (AKSS) was assessed. Data were prospectively collected on 45 cases who had single joint osteoarthritis and no other comorbidities. We have specifically focused on patients with single knee involvement to remove the effect of multiple joint involvement and comorbidities on the OKS. The mean preoperative OKS was 21.4, postoperative OKS 40.0 and postoperative ROM 117 degrees. The postoperative mean AKSS was 86.7 and mean function score was 85.0. The 'usual pain' and 'limp' components of the OKS had the greatest rises and the 'kneel' component had the least improvement. Rather than all patients achieving uniform results post-TKR, patients with more severe symptoms achieved poorer absolute outcomes. The Spearman correlation coefficient between pre- and postoperative OKS was r = 0.4 (p = 0.006). Although the results suggest that waiting too long before intervention compromises the final outcome, a correlation of 0.4 is not strong enough to necessitate change in current practice.