Kinetic Study On Knee And Its Prevention During Half-Squat Parachute Landing Based On Anybody Musculoskeletal Model

Objective To investigate the effects of two different dropping heights and knee braces on kinetics of knee joint during half-squat parachute landing(HSPL)based on the AnyBody musculoskeletal model which was established by AnyBody Modeling System soft.Besides,to provide a theoretical basis for preventing knee injury and designing knee braces.Methods 20 male active-duty paratroopers were selected to simulate HSPL with three different knee braces conditions(no brace,elastic knee brace,semi-rigid knee brace)and jump from two different dropping heights(40cm,120cm).The Vicon 3D motion capture system and force plate were used to record the kinematic data and ground reaction force(GRF),which were stored in the form of C3 D.Then the AnyBody musculoskeletal model of HSPL was established by using inertia parameters of 20 subjects in the AnyBody Modeling System.Importing C3 D data and driving the model,then analyzing the kinetic parameters of knee joint during HSPL with the technologies of computer simulation and inverse dynamics.The kinetic parameters were Peak vertical knee joint force(Peak V KRF),Peak anterior-posterior knee joint force(Peak A-P KRF),Peak medial-lateral knee joint force(Peak M-L KRF);Peak knee flexion moment(peak KFM),Peak knee abduction moment(peak KAM),Peak knee external rotation moment(peak KERM);Peak Vastus lateralis activation(Peak VLA),Peak Vastus medialis activation(Peak VMA),Peak Rectus femoris activation(Peak RFA),Peak Semitendinosus activation(Peak STA),Peak biceps femoris activation(Peak BFA).All kinetic data of knee joint were analyzed by ANOVA and paired t test,and P < 0.05 was considered statistically significant.Results 1.Dropping heights had a significant and positive effect on Peak V KRF,Peak A-P KRF,Peak M-L KRF,Peak KFM,Peak KAM,Peak KERM,Peak VLA,Peak VMA,Peak RFA,Peak STA,and Peak BFA(P < 0.05).2.Three different knee braces conditions(no brace,elastic knee brace,semi-rigid knee brace)had no significant difference on Peak knee joint force(P > 0.05).Compared with the no-brace group,use of elastic knee brace and semi-rigid knee brace at the height of 40 cm had no significant difference among Peak KFM and Peak KERM(P > 0.05),use of semi-rigid knee brace can significantly reduce Peak KAM(P < 0.05).Use of the two kinds of braces at the height of 120 cm can significantly reduce Peak KAM(P < 0.05),only semi-rigid knee brace had a effect on Peak KFM and Peak KERM(P < 0.05).3.Compared with the no-brace group,the elastic knee brace had no significant effect on Peak VLA,Peak VMA,Peak RFA,Peak STA,Peak BFA(P > 0.05),use of semi-rigid knee brace at the height of 120 cm can significantly increase Peak RFA and Peak BFA(P < 0.05).Conclusion 1.With the increase of dropping heights,the peak knee joint force,peak knee joint moment and peak muscle activation all increased,which may increase the range of motion and the instability of knee joint during HSPL,which may be the causes of knee ligament damage,knee cartilage injury,and a variety of knee joint diseases.2.Reasonable improvement of landing posture and the use of knee brace,reduce knee flexion and eversion of the dynamic load,to reduce the load of knee joint reaction force and moment during half-squat parachute landing.3.This study was the first to study the effects of different knee brace on the knee kinetics during half-squat parachute landing.The results show that,the semi-rigid knee braces can more effectively reduce the Peak KFM,Peak KAM,Peak KERM,increase the Peak RFA and Peak BFA.Thus,the semi-rigid knee braces can increase the dynamic stability of knee joint,reduce the risk of knee injuries.4.The semi-rigid knee brace has a protective effect on knee joint during HSPL,but its effect on the ligaments and menisci of knee joint is unknown.Further research should focus on the assessment of the protective effect in-depth.