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Single leg squat (SLS) is an important motion commonly observed in sports. Excessive dynamic knee valgus (DKV) during SLS may increase non-contact knee injury risks particularly in physically active females. As muscular strength plays crucial role in controlling DKV, the present study aims to evaluate the correlation between hip strength and knee frontal plane angle during SLS among females with and without excessive DKV. Thirty-four volunteers were allocated to the valgus (n = 17) and non-valgus (n = 17) groups. Their motions during SLS at 45° and 60° knee flexion were captured and analyzed using three-dimensional motion analysis system. Isokinetic hip strength was examined at 180°/s in flexion, extension, abduction, and adduction for both legs. Pearson's correlation test was computed to evaluate the relationship between hip strength and knee angle during SLS. Non-dominant hip extensor strength (r = −0.56, p = 0.02) and dominant hip adductor strength (r = −0.51, p = 0.04) were significantly related to the knee frontal plane angle during 45° SLS among those without DKV. Meanwhile, those with DKV showed a significant relationship between the knee frontal plane angle for both legs and non-dominant hip abductor strength during 60° SLS. Both groups demonstrated the relationship of hip strength on knee frontal plane angle during SLS, whereby increased hip strength may minimize excessive DKV. Those with excessive DKV should train to strengthen their hip abductor to reduce knee valgus particularly during deep squats. • Both women with and without DKV demonstrated the influence of hip strength on knee angle during SLS. • Women with and without DKV emphasize on different muscle groups at different squat depths. • In deep squats, training should focus on increasing the hip abductors strength. [ABSTRACT FROM AUTHOR]

Background The single leg squat (SLS) motion imitates various maneuvers in sports. It is commonly used as a functional test for the lower limb. SLS with two-dimensional (2-D) video analysis is regularly performed in the clinical setting to assess dynamic knee valgus (DKV). However, 2-D video analysis may not be able to demonstrate the same level of accuracy as three-dimensional (3-D) motion analysis. Purpose This study aimed to determine the within- and between-day reliability as well as the concurrent validity of 2-D and 3-D motion analysis of lower limb kinematics during 45° and 60° SLS among physically active females with and without DKV. Study Design Cross-sectional study Methods A total of 34 physically active females (17 individuals with excessive DKV and 17 without DKV) participated in the study. Their DKV was determined based on the cut-off values of knee frontal plane projection angle during drop landing. Their lower limb kinematics during SLS at 45° and 60° knee flexion were captured simultaneously by digital cameras (2-D motion capture) and infrared cameras (3-D motion capture). Intraclass Correlation Coefficient (ICC) was used as an indicator for within- and between-day reliability tests of both groups. Bland-Altman Plot and Pearson correlation were used to examine the validity of 2-D and 3-D motion capture methods in evaluating knee valgus angle. Results Two-dimensional knee FPPA and 3-D knee angle measured during 45° and 60° SLS in normal and excessive DKV groups showed moderate to excellent within-day and between-day reliability (ICC≥ 0.50). The current study showed that the 2-D knee frontal plane projection angle (FPPA) during 45° SLS were valid for the non-dominant leg in both groups. Additionally, the 2-D knee FPPA during 60° SLS were valid for non-dominant leg in excessive DKV group and dominant leg in normal group. Conclusion Two-dimensional knee FPPA during 45° and 60° SLS also showed high within- and between-day reliability for both groups. The validity of 2-D knee FPPA during SLS depends on the squat depth, stance leg, and presence of DKV. Level of Evidence 2B [ABSTRACT FROM AUTHOR]

Poor technique during landing might lead to increased risk of non-contact lower limb injuries. The purpose of the study was to evaluate the effects of landing heights and gender on the lower limb mechanics during drop vertical jump among athletes. Thirty university athletes between the ages of 19 and 25, with healthy weight, screened for a normal range of dynamic knee valgus and train regularly three times weekly were recruited as participants for the study. The lower limbs joint angles and moments were compared across gender and landing heights (30 cm vs 45 cm) at three landing time-points (initial contact, maximum vertical ground reaction force, and maximum knee flexion). The findings indicated that no significant differences were observed in lower limb joint angles and moments at the sagittal and frontal planes across gender and landing heights. Meanwhile, a significant difference existed for knee extensor moment during maximum knee flexion (F(1.618,90.629) = 4.096, p = 0.027) across landing heights. landing heights and gender may not affect lower limb mechanics except for knee extensor moments during maximum knee flexion. Females with normal range of dynamic knee valgus may exhibit a safe landing technique hence a screening test is crucial to identify its presence among female athletes. [ABSTRACT FROM AUTHOR]