Validity and Reliability of a Virtual Reality Game in Evaluating the Projected Frontal Plane Knee Angle When Landing From a Drop Vertical Jump

Objectives:To determine the validity and reliability of the peak frontal plane knee angle evaluated by a virtual reality (VR) netball game when landing from a drop vertical jump. Study Design: Laboratory. Methods: Forty participants performed 3 drop vertical jumps evaluated by 3-dimensional motion analysis and 3 drop vertical jumps evaluated by the VR game. Limits of agreement for the peak projected frontal plane knee angle and peak knee abduction were determined. Participants were given a consensus category of "above threshold" or "below threshold" based on a prespecified threshold angle of 9 degrees during landing. Classification agreement was determined using kappa coefficient, and accuracy was determined using specificity and sensitivity. Ten participants returned 1 week later to determine intrarater reliability, standard error of the measure, and typical error. Results: The mean difference in detected frontal plane knee angle was 3.39 degrees (95% confidence interval [CI], 1.03 degrees to 5.74 degrees). Limits of agreement were -10.27 degrees (95% CI, -14.36 degrees to -6.19 degrees) to 17.05 degrees (95% CI, 12.97 degrees to 21.14 degrees). Substantial agreement, specificity, and sensitivity were observed for the threshold classification (kappa= .66; 95% CI, .42 to .88; specificity = 0.96; 95% CI, 0.78 to 1.0; and sensitivity = 0.75; 95% CI, 0.43 to 0.95). The game exhibited acceptable reliability over time (intraclass correlation coefficient, ICC (3),(1) = .844), and error was approximately 2 degrees. Conclusion: The VR game reliably evaluated a projected frontal plane knee angle. Although the knee angle detected by the VR game is strongly related to peak knee abduction, the accuracy of detecting the exact angle was limited. A threshold approach may be a more accurate approach for gaming technology to evaluate frontal plane knee angles when landing from a jump.