Prospective comparative study of knee laxity with four different methods in anterior cruciate ligament tears

Background and purpose Anterior knee laxity can be evaluated using different devices, the most commonly used being the Telos®, KT1000®, Rolimeter®, and GNRB®. However, the laxity values obtained with these devices have never been compared to one another. As such, the outcomes of studies using these different knee laxity measurement devices may not be comparable. The primary purpose of this study was to determine the side-to-side laxity difference in patients with one ACL-injured knee, using each of these devices, and to compare the values obtained from each. We hypothesized that the measurements of laxity would vary depending on the device used. Methods This was a prospective study. All patients with an ACL injury, in which surgical reconstruction was planned, underwent pre-operative knee laxity measurements using four different devices. The concordance correlation coefficient (CCC) of the results was compared between the four devices. Results The study enrolled 52 patients. With regard to the values of the side-to-side differences, the KT1000® and the GNRB® obtained the most similar values (CCC = 0.51, 95% CI 0.37–0.63). The two devices with the lowest correlation were the Telos® and the Rolimeter® (CCC = 0.04, 95% CI − 0.14–0.23). The comparability was considered average for the KT1000® and GNRB® and poor for the other devices. Conclusions The knee laxity devices used in regular practice are not comparable to one another. As a result, caution must be taken when comparing results from studies using these different devices.