Correlation between the Oxford Knee and American Knee Society scores at mid-term follow-up

A sensitive and reproducible measurement of knee surgery outcomes is increasingly needed. However, it has been difficult to compare results because of numerous scoring systems and the publication of data in these systems. Our aim was to compare the more widely used American Knee Society score (AKSS) with the shorter Oxford Knee Score (OKS). The questionnaires were completed preoperatively and at 2, 5, and 10 years postoperatively. A negative correlation of -0.64 (P < .0001) between the OKS and AKSS and the Functional score at 2 years, and a correlation of -0.5 (P < .0001) at 5 and 10 years were found. However, excellent, good, fair, and poor OKS classifications did not correlate well with the AKSS grading (weighted kappa coefficient = 0.06-0.288). This study indicates that the OKS, with its easier analysis and higher compliance rate, can be used more directly to compare studies using the AKSS.