Recently, this comment was made on one of this or another similar list:

<Pronation is not a single plane movement, it is triplanar.  "It combines
components of eversion, abduction and dorsiflexion of the lower segment of
the foot in open chain.  In closed chain, the calcaneus everts under the
talus and the talus plantarflexes, adducts and glides foward on the
calcaneus.  The floor abducts and dorsiflexes
the forefoot around the mid-talar joint (MTJ) oblique axis, and inverts the
forefoot around the MTJ longitudinal axis." (Cusick, 1995) >

*** This comment is very important to note, because there is often
considerable difference of opinion regarding the disposition of the foot
during various activities.  Many authors refer quite casually to foot
problems being caused by excessive pronation or supination of the foot, but
others point out that these terms are inaccurate and should be replaced by
eversion and inversion, respectively.

That physio comment above, while correct in stressing the triplanar aspects
of "pronation", at the very least should rather have stated that "what is
commonly referred to as pronation of the foot involves triplanar actions of
the entire lower extremity."

According to the basic definitions, pronation takes place about a single axis
(along the length of the foot or hand) and simply means the turning over of
the surface of the hands or feet so that their surfaces face partially or
fully downwards, while supination refers to the turning over of those
surfaces to face upwards. In other words, pronation and supination are
defined as uniplanar actions.

On the other hand, eversion, ostensibly simply meaning a "turning outwards"
and "inversion", ostensibly meaning a "turning inwards", are terms that have
never been defined as uniplanar actions along a single given axis, since they
involve action of all joints of the lower extremities in several planes.
Eversion certainly does not refer to rotation about the axis of the leg or
the arm, since that action  is known as internal or external rotation, nor
does it refer to inward or outward displacement to or away from the midline
of the body, since those actions are adduction or abduction.  Finally,
eversion and inversion do not refer to rotation of the foot about a specific
axis of the ankle, since those actions are known as plantarflexion or
dorsiflexion.

In other words, inversion and eversion have never been defined to be any form
of uniplanar action, so it would be interesting to know where the notion
arose that regards these actions as being some special fundamental joint
action.  This view suggests that eversion and inversion, like flexion,
internal rotation and abduction, are fundamental actions about a given joint
that involve no actions about any other axes, but they are not, as the above
process of "reductio ad absurdum" has shown.

Eversion is a complex action involving pronation, lateral rotation, valgus
("knee knocking"), dorsiflexion and adduction of the various joints of the
lower extremity in open chain situations, whereas inversion involves the
inverse of all of those actions.  Presumably one could also refer to
eversion, inversion, pronation and supination of the upper extremities if one
were standing or walking on the hands, as is the case in gymnastics and
circus acts.

Thus, if one attributes knee injuries to excessive pronation, this may be
profoundly misleading, since what one believes to be simple pronation
invariably involves differing degrees of angular displacement of all joints
of the lower extremity.  For example, one may pronate with the knees pointing
directly forwards, outwards or even  inwards with significant valgus (noting
that 'pure' pronation of the sole of the foot is not possible with the knees
fully extended); the consequences for the knees will be very different.
Incidentally, the last mentioned situation represents potentially the most
harmful posture for activities such as running and squatting.

Dr Mel C Siff
Denver, USA
http://groups.yahoo.com/group/Supertraining/