Purpose

To assess measurement equivalence, inter- and intra-rater reliability, standard error of measurements (SEM) and false positive measurements (FPM) of four different knee arthrometers (KLT,Karl Storz; KIRA ,I+; KT-1000 MEDmetric Corp; Rolimeter, Aircast) in healthy patients.

Methods

Four different investigators (two advanced (AR) and two beginners (BR)) examined 12 participants with healthy knees at two time points with regards to anterior tibial translation (ATT) and side-to-side difference (SSD). Test equivalence was assessed using the TOST (two-one-sided t-test) procedure with ±1mm equivalence boundaries. Intraclass correlation coefficients (ICCs) were calculated using two-way mixed effects models. Furthermore, false positive-(SSD >3mm) and SEMs were assessed.

Results

A total of 2304 Lachman Tests were performed. Between-rater SSDs were equivalent between AR and BR raters for the Rolimeter only. Inter-rater ICC values (SSD, ATT) were graded as “poor” to “moderate” for all devices.
Equivalent test-retest results were observed for all raters using the Rolimeter, KLT and KT-1000, whereas measurement consistency with KIRA was acceptable in the advanced examiners group only. Intra-rater ICC values (Range: SSD, ATT) were graded as “poor” to “moderate” for SSD values and “moderate” to “good” for ATT. SEMs were lowest for the Rolimeter and highest for KIRA. FPM were never obtained with the Rolimeter (0%), twice (2.1%) with the KT-1000, three times (3.1%) with the KLT and 33 times (34.4%) using KIRA.

Conclusion

There is acceptable intra-rater but poor inter-rater reliability with all tested arthrometers. Measures of knee laxity are comparable between Rolimeter, KLT and KT-1000 but higher for KIRA. Clinically, the present results recommend that repeated arthrometry measurements should always be performed by the same investigators.


Keywords: knee arthrometer; anterior cruciate ligament; ACL; anterior tibial translation; side-to-side difference; equivalence testing; Lachman Test, Rolimeter, KIRA, KLT, KT1000