Test-retest reliability of repeated knee laxity measurements in the acute phase following a knee trauma using a Rolimeter

Abstract

The purpose was to examine the test-retest reliability of the Rolimeter measurement procedure in the acute time phase, following a substantial knee trauma. In total, 15 participants with acute knee trauma were examined by one single observer at three different time-points with the Rolimeter using a maximum force. The selected time-points were: baseline (0-7 days after the trauma), midpoint (3-4 weeks after the trauma), and endpoint (3-4 weeks after the trauma). The anterior-posterior displacement was recorded where the endpoint evaluation was used as the reference value. The mean anterior laxity scores remained constant over the measurement time-points for both knees, with an anterior laxity that was 2.7 mm higher (on average) in the injured than the noninjured knee (9.5 mm vs. 6.8 mm). The mean difference (i.e., bias) between laxity scores, for the injured knee, measured at endpoint versus baseline was 0.2±1.0 mm and -0.2±1.1 mm when measured at endpoint versus midpoint, with average typical errors of 0.7 and 0.8 mm and intra-class correlations that were very strong (both r=~0.93). For the same comparisons on the noninjured knee, systematic bias was close to zero (0.1±0.3 and -0.1±0.3 mm, respectively), and both the intra-class correlations were almost perfect (r=~0.99). The current study implicates that repeated Rolimeter measurements are relatively reliable for quantifying anterior knee laxity during the acute time-phases following knee trauma. Hence, the Rolimeter, in combination with manual tests, seems to be a valuable tool for identifying anterior cruciate ligament injuries.

Keywords: Anterior cruciate ligament; Arthrometer; Hemarthrosis; Instability; Knee joint.

Fig. 1

The arthrometer, Rolimeter Aircast Europa, with leg and foot support.

Fig. 2

The Rolimeter measurement starting position.

Fig. 3

Bland-Altman plots (left) and corresponding intraclass correlations (right) for the anterior knee-displacement (i.e., laxity) scores, using Rolimeter readings, at different time-points after acute knee trauma: (A) injured knee, endpoint vs. baseline, (B) injured knee, midpoint vs. baseline, (C) noninjured knee, endpoint vs. baseline, and (D) noninjured knee, midpoint vs. baseline. Measurements at baseline, midpoint and endpoint were performed 0–7 days, 3–4 weeks, and 6–8 weeks after the trauma, respectively. Bland-Altman plots represent the mean difference in the anterior knee displacement (i.e., systematic bias) ±95% (1.96 standard deviation [SD]) limits of agreement (LOA) between the time-points. Dashed lines in the intraclass correlations represent the lines of identity.