Concurrent validity between two-dimensional and three dimensional motion systems for evaluation of frontal plane knee kinematics during a drop vertical jump task
Figueroa Ayala, Carla N.
Seda Díaz, Alexie H.
Rodríguez Lafontaine, Alejandro
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Identifying increase risks for ACL injuries and PFPS have become essential in order to decrease its incidence in the recreational and competitive athlete. Risk factors predisposing to lower extremity injuries have been identified using motion analysis system. 3D motion analysis is considered the gold standard for kinematic analysis of the lower extremities, but its highly instrumented nature makes it difficult to be used as a preventive screening tool. Alternatively, 2D video system could serve this purpose. Therefore, the aims of this study are to establish the concurrent validity and intrarater/interrater reliability of four different 2D video-based techniques. It was hypothesized that all 2D measures were reliable (ICC >0.80) and highly correlated (ICC>0.80) with the 3D system for the outcomes of interest. All four 2D measures showed good to excellent interrater and intrarater reliability with ICC values ranging from 0.82 to 0.97. Knee to ankle separation (KASR) and knee separation distance (KSD) showed excellent correlation with ICC value of 0.91 and 0.88 respectively, while both method of frontal plane projection angle (FPPA) showed non to poor correlation with ICC values ranging to 0 to 0.40. 2D and KSD are comparable with 3D measures indicating that a 2D cost-effective reliable and valid screening for dynamic knee valgus can be established.