Description
Objectives:
The measurement of knee laxity is crucial to diagnose and evaluate the degree of anterior cruciate ligament (ACL) injuries. Several devices have been investigated to quantify knee laxity, but poor reproducibility and unreliable results have been reported. KNEELAX3 is a device to measure anterior tibial translation (ATT) in millimeters recording procedure with computerized software. The aims of this study were to measure ATT of healthy Japanese women using KNEELAX3 and to determine the reliability and validity of the KNEELAX3.
Methods:
Sixty healthy Japanese women with no history of knee pathology (mean age 27.1 ± 3.6years) were included in this study. Three examiners (A, B, C), who were skilled in the use of KNEELAX3, measured the ATT under a 132N load. Each subject was positioned supine on an examination table with the knee in approximately 20 degrees of flexion. For calculation of mean values and analysis of intra-rater reliability, examiner A performed measurements twice on the same subjects on different days. For analysis of inter-rater reliability, three examiners measured on the same day. In order to analyzed inter-rater and intra-rater reliability, the intraclass correlation coefficient (ICC) was performed, and Bland-Altman (BA) analysis was used to determine the systematic error.
Results:
The mean ATT was 5.5±1.8mm on the right side and 6.4±1.8mm on the left side. The ICC (95% CI) for intra-rater reliability were 0.75 (0.62-0.85) on the right and 0.88 (0.80-0.92) on the left. Based on the results of BA analysis, there was no systematic error and the MDC95 were 2.58mm on the right and 1.84mm on the left. The ICC for inter-rater reliability were 0.76 (0.60-0.86) on the right and 0.87 (0.81-0.92) on the left. The BA analysis showed the fixed error in the right knee between examiner A and the other examiner, while there were no systematic errors between the other examiners. The ICC for intra-rater reliability of the side-to-side difference was 0.56 and MDC95 was 2.11mm, and the ICC for inter-rater reliability of the side-to-side difference was 0.44, and MDC95 was 2.01-2.37mm: The fixed error was observed for examiner A, but no fixed error was confirmed for other examiners. No proportional error was observed in any of the measurements for each analysis.
Conclusions:
This study demonstrated that there were good intra-rater reliability and moderate to good inter-rater reliability of measuring ATT using the KNEELAX3 in healthy women. However, the fixed error was found between one examiner and others, whereas no proportional error was found in any of the measurements. There was no deviation proportionally to the true value or occurred in a specific direction. Based on the results in this study, the measurement of ATT with use of KNEELAX3 is reliable, but the measurement technique should be standardized and established in consideration of the physical characteristics of the subjects to minimize the measurement errors.
