Comparison Of Post-ACLR Kinematics Between Landings Of A Drop Vertical Jump

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The drop vertical jump (DVJ) task is used to assess functional recovery after an anterior cruciate ligament reconstruction (ACLR). A DVJ has two distinct phases, and while the 1st landing is more commonly analyzed, the 2nd landing follows a maximal jump and may better represent higher-risk sport situations. Comparing the kinematics of each landing in subjects after an ACLR would provide insights into the specific qualities of each landing to inform clinical examination and future research. PURPOSE: To compare hip and knee kinematics of the reconstructed limb between the 1st and 2nd landing of a DVJ in patients after ACLR. METHODS: 22 subjects (10 F, age 20.6±5 y, H 1.7±0.1 m, M 71±12 kg) 6 months post-ACLR performed a DVJ. Subjects were asked to step off of a 30.5 cm box, land (1st landing), maximally jump, and land once more (2nd landing) during an instrumented data collection. Visual 3D was used to calculate hip and knee kinematics at initial contact. Paired sample t-tests were used to compare between landings. RESULTS: The ACLR limb demonstrated less knee flexion but greater knee abduction and internal rotation angles during the 2nd landing (Table 1). The hip exhibited less flexion and internal rotation motion. No differences were observed in frontal plane hip motion. CONCLUSION: The 1st and 2nd landings of a DVJ require distinct kinematics of the ACLR limb. Less knee flexion combined with greater knee abduction and internal rotation of the ACLR limb during the 2nd landing suggests that this landing better detects abnormal mechanics associated with subsequent injury risk. Thus, the 2nd landing could warrant additional study to identify patients who may be at greater risk for re-injury after ACLR.Table 1: Kinematic variables at foot strike during 1st and 2nd landings of a drop vertical jump