Pronation, Eversion and Other Friends

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Recently, this comment was made on one of the physio lists:

<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

Supertraining/