Knee Frontal Plane Projection Angle: A Comparison Study Between Drop Vertical Jump and Step-Down Tests With Young Volleyball Athletes

Study Design: Observational study. Context: Altered frontal plane knee mechanics during dynamic tasks have been often associated with lower-extremity injuries. Strategies to decrease these risk factors and improve knee joint stability are often applied in rehabilitation and training environments. Objective: The purpose of this study was to compare knee joint frontal plane projection angles (FPPA) via 2-dimensional video analysis during drop vertical jump (DVJ) and step-down test (SDT) tasks in the preferred and nonpreferred limbs of young male and female volleyball players. Methods: A total of 60 young male (n = 29) and female (n = 31) volleyball players (13.6 [1.1] y, 62.2 [11.2] kg, and 170.8 [10] cm) participated in this study. Once the athletes were screened for inclusion and exclusion criteria, limb preference was operationally defined as the preferred kicking leg or the foot used for stair climbing. In a randomized study design, participants were asked to perform a bilateral DVJ and unilateral step-down landing tasks for both preferred and nonpreferred limb. Kinematic analysis was performed via a 2-dimensional video recording of knee joint FPPA alignment. Results: No difference was noted in FFPA during DVJ and SDT tasks between preferred and nonpreferred limbs in both male and female groups (P >.05). The FFPA was significantly higher for both limbs during DVJ versus SDT in both groups (P <= .05), but it was not different between male and female athletes. Conclusions: Based on these findings, clinicians may expect young male and female volleyball athletes to demonstrate similar and symmetrical lower-extremity 2-dimensional knee joint FPPA values across screening tests intended to identify lower-extremity injury risk factors. However, greater FPPA values should be expected during the more dynamic DVJ task.