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Document Title: Yu-CB-Mar06.shtml
Article Title: Lower extremity biomechanics during the landing of a stop-jump task
Authors: Bing Yu, Cheng-Feng Lin, William E. Garrett
Publication: Clinical Biomechanics
Date: March 2006
Volume 21, Number 3, pages 297-305
Keywords: Female athlete knee-injury prevention, biomechanics, kinetics, knee motion, kinematics, forces, moments, torques,
(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)
Comments: This study found that more motion at the hip and knee translates into lower potentially-ACL-injurious forces. This makes sense intuitively as well: anyone who lands a jump with knees locked at full extension or hyperextension is guaranteed to incur massive, permanent, severe injuries to the knee ligaments and articular cartilage. The take-home message here is to always land jumps with ample knee flexion.
Abstract
Background
Literature shows that landing with great impact forces may be a risk factor for knee injuries. The purpose of this study was to examine the relationships among selected lower extremity kinematics and kinetics during the landing of a stop-jump task.
Methods
Landmark coordinates and ground reaction forces during a stop-jump task were collected. Lower extremity joint angles and resultants were reduced. Pearson correlation coefficients among selected lower extremity kinematics and kinetics were determined.
Findings
The hip flexion angular velocity at the initial foot contact had significant correlation with peak posterior and vertical ground reaction forces (r = -0.63, P < 0.001, r = -0.48, P < 0.001) during the landing of the stop-jump task. The knee flexion angular velocity at the initial foot contact also had significant correlation with peak posterior and vertical ground reaction force (r = -0.49, P < 0.001, r = -0.06, P < 0.001) during the landing of the stop-jump task. Peak proximal tibia anterior shear force and peak knee extension moment during landing of the stop-jump task had significantly correlation with the corresponding posterior and vertical ground reaction forces (r > 0.51, P < 0.001).
Interpretation
A large hip and knee flexion angles at the initial foot contact with the ground do not necessarily reduce the impact forces during the landing of the stop-jump task, but active hip and knee flexion motions do. Hip joint motion at the initial foot contact with the ground appears to be an important technical factor that affects anterior cruciate ligament loading during the landing of the stop-jump task.
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