Biomechanical Study Of The Knee Joint Protection In Overweight And Obese People

Background and objectivesObesity may augment the risk of sport injury to the knee joints and is a significant risk factor for musculoskeletal disorders,such as knee osteoarthritis(KOA).It is important to enhance knee protection for obese and overweight people.There is a need to maintain normal knee biomechanical characteristics of obese and overweight people during exercise.The drop jump is used to screen for abnormal movement patterns in an attempt to identify the risk of knee injury,but few studies have explored the biomechanical differences between the overweight/obese people and healthy people for the drop jump.In addition,cushioning insoles have been used as knee-protection aids.A previous study found cushioning insoles could effectively protect knee joints with meniscal injuries.However,whether cushioning insoles can protect the knee joints of obese and overweight people more effectively remains unknown.Therefore,the main purpose of this study were to explore the knee biomechanical characteristics of drop jump in overweight/obese people and to investigate the effects of insoles with different cushioning properties on the knee joints of people with different body mass index(BMI)grades based on the analysis of insole cushioning properties and knee kinematic and kinetic variables.Methods1.15 participants were recruited from the healthy weight group,16 from the overweight group and 15 from the obese group.Based on the three-dimensional motion capture system and the force measuring table,the knee kinematic and kinetic data of all participants at the critical moments of the 30cm drop jump were collected and analyzed,and the biomechanical differences of the knee joints in different BMI groups were evaluated.2.A gravity-driven impact test was used to characterize the cushioning properties of three types of Artificial Cartilage Foam(ACF18,28,and 38)and ethylene-vinyl acetate(EVA)insoles according to ASTM-F1976-13.Biomechanical data were collected from healthy weight(n=15),overweight(n=16),and obese(n=15)individuals randomly assigned four different insoles during a drop jump.Statistical analysis was used to compare differences among cushioning parameters and biomechanical data from different insoles.Results1.Compared with healthy people,peak vertical ground reaction force of overweight people increased,and the knee flexion motion and rotation moment decreased(all P<0.05);the adduction angle and power of knee joints and vertical ground reaction force increased(all P<0.05),and knee flexion motion,rotation moment and propulsion time decreased in obese people(all P<0.05).Compared with overweight people,obese people had lower knee flexion motion(P<0.05).2.For insole cushioning,ACF was significantly better than EVA,and ACF38 was the best among the three types of ACF.In the healthy weight group,all ACF insoles decreased the knee flexion moment(all P<0.05),and the ACF38 insoles decreased the adduction moment compared with the EVA insoles(P=0.023).In the overweight group,the ACF insoles decreased the knee adduction angle and moment(all P<0.05).The knee rotation moment at the second contact was lower in the ACF38 insoles than in the EVA insoles(P=0.020).In the obese group,the ACF insoles had lower knee flexion angle and moment and extended cushion time(all P<0.05).The knee rotation moment(P=0.033)was lower and the cushion time(P=0.044)was longer for the ACF38 insoles than those for the ACF18 insoles.Conclusion1.There were differences in knee kinematics and kinetics between overweight,obese and healthy people in drop jump,suggesting that overweight and obese people may have biomechanical abnormalities in knee joints.2.Insoles with better cushioning properties could improve knee biomechanics,which may provide better protection for the knee joints of people,especially overweight and obese people.