The bones and soft tissues of the foot act as a shock attenuator and the relative bony motions of the talocrural and subtalar joints are the subject of research interest for their roles in lower extremity pathology. Despite this interest, little information exists on the precise in vivo talocrural and subtalar joint kinematics during dynamic activities. Therefore, the purpose of this study was to quantify the three-dimensional kinematics of the talocrural and subtalar joints during landing by using single-plane fluoroscopic imaging and shape matching techniques. Three-dimensional bone positions for 6 subjects during landing from a 10 cm height were determined by using 3D-2D model-image registration techniques. The primary talocrural joint motion after toe contact was dorsiflexion with rotation ranges averaging 12° ± 7° dorsiflexion, 2° ± 2° eversion, and 3° ± 2° internal rotation. The subtalar joint exhibited similar patterns of increased dorsiflexion, eversion, and external rotation up to 150 ms after landing. The angular changes were 5° ± 3° dorsiflexion, 7° ± 3° eversion, and 6° ± 2° external rotation. This study contributes to the quantitative understanding of the function of the normal talocrural and subtalar joints and can be used for comparison with data obtained from injured feet.
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