what-when-how
In Depth Tutorials and Information
Key Concept
The foot is a highly dynamic structure whose form or shape under
static conditions does not reflect the movements it performs during
walking and running. Assessment of shape or posture therefore has
limitations in respect of what that can tell us about foot function during
activity.
terminology for movement and position of the foot
This may seem a quite obvious and redundant topic but in fact there are
great national variations in foot and ankle biomechanics terminology.
There is little formally and widely agreed consensus, but there is much
copying of good (and bad) practice.
As with all human joint movements and joint positions, those of the
foot are described in the sagittal, frontal and transverse planes; however,
there is an issue in whether these are defined within the foot, or within
the same planes as they are defined for the entire body ( Figure 1.1 ). This
causes particular problems for movement descriptions in the sagittal and
frontal planes. This is because the feet are abducted in the transverse
plane by a variable amount between people. If foot motion is described
in the sagittal plane of the body, then the relationship between the foot
anatomy and the body planes will vary between people, and this largely
defeats the purpose of having standardized planes of motion. The same
occurs for frontal plane motion.
As an alternative, sagittal, and frontal, planes can be defined within the
foot ( Figure 1.2 ). That is to say, the reference points from which planes
are defined are taken from foot anatomy rather than from the whole body
anatomy. In this case, the sagittal plane is defined as perpendicular to
the supporting surface and aligned anterior/posterior with a line between
the centre of the second metatarsal head and the centre of the posterior
calcaneus. It follows that the frontal plane is perpendicular to both trans-
verse and sagittal planes, and should therefore lie parallel to the posterior
surface of the calcaneus.
Notably, using these definitions allows an important link to be created
between experimental biomechanics data on foot motion and clinical
terms of reference for foot motion.
Sagittal plane motion is referred to as dorsiflexion (lifting the distal
segment of a joint towards the front of the tibia) and plantar flexion
(dropping the distal segment of a joint away from the front of the
tibia).
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