## 4 Discussion
Therefore, as with stiff landings [1], landing in the knee valgus position appears to result in greater energy absorption in the knee joint. In addition to demonstrating that the knee experienced the greatest impact load in the valgus position, we also showed that negative mechanical work at the hip and knee had positive and negative correlations with the knee valgus angle, respectively. This suggested that an increase in the knee valgus angle during landing may reduce the contribution of the hip joint to energy absorption and that there is an associated reciprocal increased contribution by the knee joint. [PERSON] et al. revealed a relationship between increased knee valgus and decreased gluteus maximus engagement, which is related to sagittal plane hip joint motion, during single-leg squat maneuvers [40; 41]. They indicated that gluteus maximus recruitment may be associated with an improvement of knee valgus alignment in females. Furthermore, [PERSON] et al. and [PERSON] et al. indicated that the hip joint of females, who have larger knee valgus than males during landings [42; 43], was a poor contributor to energy absorption compared with the knee and ankle joints. We therefore conclude that landing in a knee valgus position is a key biomechanical factor that increases the contribution of the knee joint to energy absorption, and that this can be prevented by adopting a knee varus position during landing, thereby absorbing the impact in hip extensors, such as the gluteus maximus. Furthermore, reduced impact in hip extensors during landing in the knee varus position can prevent the progression of knee cartilage change caused by sustained mechanical stress for a long period of time. During DP of the DVJ, the angles in the lower extremities were not affected by the difference in the frontal knee alignment. Thus, landing in the valgus position influenced the kinetics and energetics in the lower extremities (i.e., angular impulses in the lower extremities, the hip and knee negative mechanical works, and the joint moments) without altering alignment in the sagittal plane. These findings suggest that it is not sufficient to evaluate lower extremity kinematics alone when assessing impact attenuation during landing, but that combining kinetic and energetic evaluations of the hip and knee joints could help when assessing the mechanical load in the knee joint and energy absorption in the lower extremity joints. When evaluating the landing strategy and energetic characteristics in subjects who land in the valgus, these considerations may be useful. Some limitations to this study should be noted. First, we focused on the energy absorption strategy in the lower extremities in the sagittal plane because motion in this plane has been shown to make a greater contribution to energy absorption than that in the frontal plane. An area for future study exists in assessing the energy absorption strategy in the frontal plane during landing in the knee valgus position. Second, we had a small sample size per group after group categorization, therefore, it could be argued that the results of this study might not provide an accurate measure of the difference in characteristics related to energy absorption between the two knee alignments during landing. In order to mitigate the effects of sample size, we calculated the ES for all the analyses. This enabled us to illustrate the magnitude of the differences between the groups more meaningfully. Analysis of the hip and knee angular impulses and mechanical work resulted in a medium ES of more than 0.3, which indicates that, despite the small sample size, our results provide a useful comparison of the differences in energy absorption strategies in lower extremity joints between the two landing postures.