Protective Knee Braces and the Biomechanics of the Half-Squat Parachute Landing

Knee injuries are common among paratroopers and skydivers during landing maneuvers. The aim of this study was to investigate the effects of dropping height and the use of protective knee braces on parachute landing biomechanics.

The study cohort consisted of 30 male elite paratroopers with formal parachute landing training and more than 2 yr of parachute jumping experience. Each participant was instructed to jump off a platform at two different heights (40 and 80 cm, respectively) and land on force plates in a half-squat posture. All participants tested three different knee brace conditions (no-brace, elastic brace, and semi-rigid brace) at each height.

With an increase in dropping height, peak vertical ground reaction forces (GRF), peak flexion angle, peak flexion angular displacement, peak abduction angle, peak abduction angular displacement, peak extorsion angle, and peak extorsion angular displacement of the knee joint all increased. As compared without the use of a brace, use of an elastic or semi-rigid knee brace significantly reduced peak flexion angle, peak flexion angular displacement, peak abduction angular displacement, and peak extorsion angle, while there were no significant differences in peak vertical GRF or peak extorsion angular displacement. The semi-rigid brace provided the greatest restriction against peak abduction angle (3-6°).

The elastic and semi-rigid knee braces both effectively restricted motion stability of the knee joint in the sagittal and coronal planes. The semi-rigid brace had a more marked effect, although the comfort of this device should be improved.Wu D, Zheng C, Wu J, Wang L, Wei X, Wang L. Protective knee braces and the biomechanics of the half-squat parachute landing. Aerosp Med Hum Perform. 2018; 89(1):26-31.