Kinematics and kinetics of lower-extremity joints in parachuting landing with backpack and knee brace.

Injuries on lower-extremity joints were caused by high impact force in parachuting landing. Knee brace was used to protect knee by restraining motion of knee. Backpack was necessary in parachuting landing and would increase lower-extremity joints injuries. This study aimed to analyze kinematics and kinetics of hip, knee and ankle for investigating multi-joint protection of knee brace for those joints in parachuting landing with backpack. Seven participants landed from 120 cm height. Kinematics and kinetics of hip, knee and ankle were analyzed. It was found that without backpack knee brace decreased angular displacements of hip (12.0%), knee (10.3%) and ankle (18.6%) on sagittal plane and angular velocities of hip (11.9%), knee (6.6%) and ankle (20.9%) on sagittal plane. With backpack, knee brace decreased angular displacement (5.5%) and angular velocity of knee (6.2%) on sagittal plane, but did not significantly influence those of hip and ankle on sagittal plane. Ground reaction force, joint moments and joint energy absorptions were not significantly influenced with knee brace. In conclusion, in parachuting landing without backpack, knee brace could provide multi-joint protection for hip, knee and ankle. In parachuting landing with backpack, knee brace could still protect knee, but could not protect hip and ankle.