What If You Cannot See and Do Not Know? The Effects of Vision and Knowledge of Landing Heights on Single-Leg Prelanding and Early Landing Mechanics.

Anterior cruciate ligament (ACL) injuries commonly occur during unbalanced single-leg landings, where inadequate anticipation and response to ground contact might increase risk. Vision and knowledge of landing heights may influence how athletes anticipate and respond to landings. This study examined the effects of the removal of visual input and knowledge of landing heights on knee biomechanics associated with ACL injury risk. Thirty-three recreational athletes performed single-leg landings from 3 different heights (11, 22, and 33 cm) under 3 conditions: with both vision and knowledge, with knowledge but without vision, and without both. The no vision and no knowledge condition resulted in an intermediate strategy that produced similar landing mechanics for 22 cm but significantly different kinematics and kinetics for 11 and 33 cm. Slower knee flexion angular velocities, increased peak vertical ground reaction forces, and greater knee internal rotation and abduction angles suggested increased ACL loading for 33 cm. Landing patterns with knowledge but without vision closely matched those with both. Removing both vision and knowledge significantly altered landing mechanics, emphasizing the need to train athletes to accurately anticipate initial contact of landings and adopt safe landing strategies under restricted visual and uncertain or perturbed conditions.