Introduction: The likelihood of sustaining an ACL injury in a noncontact situation is two to eight times greater for females than for males. However, the mechanism and risk factors of ACL injury are still unknown. Therefore, the aim of current study was evaluation of lower extremity kinematics and shock absorption during single- leg landing between male and female athletes.
Methodology: Fifteen female (20.1±1.5 years old) and eighteen male (21.6±1.9 years old) volunteered to participate in the experiment. At first, seven passive reflective markers were attached on the right foot of each subject (dominant leg of all subjects were right leg). Then the participant stand on the platform with height 60 cm while your hands were on the pelvic, and then with dominant leg performed the single leg drop landing. The processes of the landings were recording by using of optoelectronic 3D motion analysis with 6 cameras, and then the recording data were analyzed by cortex software. The parameters of knee angle in the sagittal and frontal planes at the moment of the landing, the maximum knee angle in the sagittal and frontal planes after landing and maximum tibial linear acceleration, were measured. Statistical analysis of the data was performed by SPSS v23 software and using independent sample t-test at the level of 0.05 significance.
Results: Results of independent sample t-test showed that at the moment of foot contact, female landing with more extended knee (22.6±4.92 vs 34.2±7.92 degree of flexion, P<0.001) and landing with larger valgus angle than male (2.3±3.28 degree of valgus vs 1.7±2.65 degree of varus, P=0.128). Maximum flexion of knee angle after landing was in the female 37.01 degree and in the male 60.33 degree (P<0.001), and at this moment knee valgus angle in female and male was 3.9±3.61 and 2.8±3.27 degrees respectively (P=0.265). Also, the parameter of maximum tibial linear acceleration showed that significant difference between female and men (5.19±1.22 g vs 4.03±0.98 g, P=0.042).
Discussion: The main factors of ACL injury in the noncontact situations are the landing with extended knee, increase in valgus and also the inability to adjust of the acting forces on the body. The results of this study showed that during single leg drop landing, female than male have less knee flexion angle, larger valgus angle and greater tibial linear acceleration. Thus, inappropriate landing mechanism can be one of the main reasons of increased ACL injury in female than male.