Differences between the sexes in knee kinetics during landing from volleyball block jumps

The aim of the study was to assess frontal and sagittal plane kinetics (normalized ground reaction force and normalized knee moment) in male and female university volleyball players when performing opposed block jump landings. Females displayed a significantly lower normalized knee extension moment at the start of muscle latency than males. The greater normalized knee extension moment at the start of muscle latency in females suggests that, through practice, they may have developed a landing strategy that minimizes the moment acting about the knee in the sagittal plane to reduce the likely strain on the passive support structures. The time histories of the normalized knee moment in the frontal plane were different between males and females. The maximum normalized knee valgus moment was significantly greater in females than males. The significantly different maximum normalized knee valgus moment between males and females indicates a greater likelihood of overloading the muscles of the knee in females during landing, which, in turn, is likely to increase the strain on the passive support structures. The increased likely strain on the passive support structures of the knee in females could contribute to the higher incidence of non-contact anterior cruciate ligament injury in females compared with males.