Test–Retest Reliability of a New Device Versus a Long-Arm Goniometer to Evaluate Knee Proprioception

Context : Many methods used to evaluate knee proprioception have shortcomings that limit their use in clinical settings. Based on an inexpensive 3D camera, a new portable device was recently used to evaluate the joint position sense (JPS) of the knee joint. However, the test–retest reliability of the new method remains unclear. This study aimed to evaluate the test–retest reliability of the new device and a long-arm goniometer for assessing knee JPS, and to compare the variability of the 2 methods. Design : Prospective observational study of the test–retest reliability of knee JPS measurements. Methods : Twenty-one healthy adults were tested in 2 sessions with a 1-week interval. Three target knee flexion angles (30°, 45°, and 60°) were reproduced in each session. Target and reproduced angles were measured with both methods. Intraclass correlation coefficients, standard error of the measurement, and Bland–Altman plots were used to quantify test–retest reliability. Paired t tests were used to compare knee JPS (absolute error of the target-reproduced angle) between the methods. Results : The new device (good to excellent intraclass correlation coefficients .74–.80; standard error of the measurement 0.52°–0.61°) demonstrated better test–retest reliability than the goniometer (poor to fair intraclass correlation coefficients .23–.43; standard error of the measurement 0.89°–2.07°) and better test–retest agreement (respective mean differences for the 30°, 45°, and 60° knee angles: 0.11°, 0.13°, and 0.41° for the new system; 0.84°, 1.52°, and 1.18° for the goniometer). The measurements (absolute errors of the target-reproduced angles) with the goniometer were significantly greater than those with the new device ( P < .05); the SDs of repeated measurements with the goniometer (1.50°–2.41°) were greater than with the new device (1.08°–1.38°). Conclusions : Given that the new device has good reliability and sufficient precision, it is the better alternative for evaluating knee JPS. Goniometers should be used with caution to assess knee JPS.