Relationship between quadriceps strength and landing kinematics

ACL injury is a common orthopaedic injury in many sports. Athletes suffering an ACL injury usually require financially costly surgical procedure, as well as, a timely recovery period and increased chance of developing arthritis in the injured knee. In game video analysis of non-contact ACL injuries has revealed a low knee flexion angle at initial contact with the ground of the injured knee as a common mechanism for injury. To prevent extended knee landing kinematics, athletes must possess adequate strength to control the downward accelerations and resultant moments at the hip and knee joints. Therefore, this study examined if a relationship exists between knee flexion angle and quadriceps strength during three jump conditions. Twenty-eight (N=28) participants’ dominant leg, knee flexion angle at initial contact with the ground was measured from three different jump conditions via 3-D motion capture system. Participants’ quadriceps strength was also measured utilizing an isokinetic (60˚/sec) dynamometer. To correct for different body masses and sizes of our male and female participants, we normalized the strength data to body weight. Results of the study did not show a significant, positive relationship between knee flexion and quadriceps strength, when normalizing strength to body weight, in either male or female participants or combined as one cohort, for any of the three jump conditions. We concluded that our normalizing factor was flawed and that our findings are inconclusive at this time.