A cross-sectional study to assess variability in knee frontal plane movement during single leg squat in patients with anterior cruciate ligament injury.

BACKGROUND: Single leg squat (SLS) tests help predict anterior cruciate ligament injuries. However, the variability in joint movement during this test has not been fully investigated. The aim of this study was to examine the knee frontal plane movement variability during SLS in patients with anterior cruciate ligament (ACL) injury. METHODS: In this cross-sectional study, we enrolled 56 patients with ACL injury (28 males; 28 females) and 46 healthy subjects (23 males; 23 females). All participants underwent SLS tests. All kinematic variables were joint angle of trunk, pelvis and lower limb, center of gravity (COG), center of pressure (COP). These data were obtained at the frontal plane and the coefficient of variation (CV) were calculated. Multiple comparisons were performed between healthy subjects and the injured leg and uninjured leg of patients with ACL injury. The correlation of the CV in knee varus/valgus range of motion (ROM) with the CV in other kinematic variables were investigated in patients with ACL injury. RESULTS: Compared with healthy subjects, patients with ACL injury exhibited significantly larger the CV in knee varus/valgus ROM. A positive correlation was observed between the CV in knee varus/valgus ROM and the CV in pelvic lateral inclination ROM in patients with ACL injury. CONCLUSIONS: Knee frontal plane movement variability during SLS may help evaluate the risk of ACL injury/re-injury. In addition, pelvic lateral inclination variability during SLS may need to be evaluated in conjunction with knee frontal plane movement variability.

Lower limb kinematics of single-leg squat performance in patients with anterior cruciate ligament deficiency.

[Purpose] This study investigated the parameters that characterize the knee, hip, and pelvic kinematics during a single-leg squat in preoperative anterior cruciate ligament rupture injury. [Participants and Methods] Overall, 15 patients with unilateral anterior cruciate ligament deficiency were enrolled in this study. For each single-leg squat, data from two-dimensional video cameras and three-dimensional motion analysis were collected. Measurement indices included the articular angles of the knee, hip, and trunk. The anterior cruciate ligament-injured leg was compared with the uninjured leg. [Results] The maximum knee valgus and flexion angles during a single-leg squat were smaller in the injured leg than in the uninjured leg. During the single-leg squat, the effect of "compensatory mechanisms" appeared as knee valgus and flexion movements. In particular, the knee valgus angle decreased in the anterior cruciate ligament-injured leg compared to that in the uninjured leg. [Conclusion] This phenomenon suggests that it is possible to utilize recurrence prevention training for anterior cruciate ligament injury.

Joint movement variability during landing in patients with anterior cruciate ligament reconstruction.

BACKGROUND: Rapid knee valgus and knee internal rotation motions in the initial phase of landing are the known mechanisms for anterior cruciate ligament injury, and many studies have been investigated on knee joint peak angle during landing. However, the variability in joint movement during landing has not been fully investigated. This study aimed to compare the coefficient of variation of lower extremity range of motion in patients with anterior cruciate ligament reconstruction and healthy subjects during landing. METHODS: In this cross-sectional study, 54 patients with anterior cruciate ligament reconstruction and 44 healthy subjects were enrolled. All participants underwent six trials of single-leg hop landing for maximum safe horizontal distance. The kinematic variables were the coefficient of variation during two discrete (0.05 after initial contact and maximum knee flexion) time points for selected three-dimensional hip and knee joint range of motion. Comparisons were performed between the two groups. RESULTS: Compared with healthy subjects, patients with anterior cruciate ligament reconstruction had greater the coefficient of variation in hip internal/external rotation range of motion (patients with anterior cruciate ligament reconstruction had 41.9%, healthy subjects had 25.5%; P=0.0018; effect size: 0.32) and knee internal/external rotation range of motion (patients with anterior cruciate ligament reconstruction had 68.4%; healthy subjects had 48.1%; P=0.0014; effect size: 0.32) for periods that spanned 0.05 s from the initial contact. CONCLUSIONS: Patients with anterior cruciate ligament reconstruction could be disadvantageous in ability to control and adapt hip and knee joint rotations when controlling landings.