Biomedical Engineering Reference
In-Depth Information
Fig. 4.4
Infinity of Instantaneous Axes of Tibiotalar Rotation [1]
joints. Fortunately, for purposes of analysis and design the complex motion
degrees can be reasonably approximated by a planar plantar - dorsiflexion [2],
axial (Internal - External) rotation and inversion-eversion.
The five degrees of freedom associated with the tibiotalar joint are:
Plantar - dorsiflexion; which is the principal motion of the joint.
Axial rotation; which motion is limited primarily by the mortise and ligaments
of the ankle.
Inversion - Eversion (I-E); which motion is limited by the ligaments and the
tibiotalar articulating surfaces.
Anterior - posterior (A-P) translation; which motion is limited by the ligaments
and the tibiotalar articulating surfaces.
Medial - Lateral (M-L) translation; which motion is limited by the mortise.
The first two are primarily associated with ankle motion and the remaining
primarily with ankle stability.
These are illustrated in Fig. 4.5.
