2. Talocalcaneal Subluxation

The calcaneus can sublux into inversion or eversion under the talus. Inversion subluxations often result from inversion injuries of the ankle especially where the weight is taken through the heel rather than the cuboid area. Eversion subluxations may result from over-flattening of the foot for whatever reason.

Anatomy and Biomechanics

This is structurally a modified ovoid joint but functionally it is a modified sellar. The reason for this is that the joint is essentially two joints in one. The superior surface of the calcaneus is concave anteriorly while posteriorly it is convex. As both surfaces have to move simultaneously, it means that they effectively form a concavoconvex or sellar surface. Consequently this joint has only one degree of freedom, inversion and eversion. During inversion, the anterior surface being concave moves with the osteokinematic that is medially while the posterior surface moves in the opposite direction, that is laterally.

The collateral ligaments of the ankle, small talocalcaneal ligaments and the two bands of the interosseus ligament afford stability of the joint particularly the posterior.

Examination Findings

Inversion subluxations are characterized by a loss of passive physiological eversion, especially the roll laterally at the end of the movement. The end feel is jammed (i.e. abrupt and hard). The arthrokinematic of posterior talar gliding is also jammed. Eversion subluxations are recognized by limited physiological inversion and anterior talar gliding, again both with a pathomechanical end feel. Either subluxation may occur at the anterior or posterior joint surface with the anterior perhaps being more common. To determine which joint surface is affected, medial and lateral glides are performed across the joint. The posterior calcaneus presents a convex surface to the talus so if this surface is glided laterally, it tests the medial osteokinematic that is inversion and if glided medially, eversion. The anterior joint surface of the calcaneus is concave so the arthrokinematic and osteokinematic are in the same direction. Consequently, a medial glide tests inversion and a lateral eversion.

Technique

Eversion Manipulation (Inversion Subluxation)
The patient lies on their side with the medial border of the affected foot upwards. The therapist sits on the bed with his or her back towards the patient. The foot is held so that the thumbs are positioned over the lateral aspect of the calcaneus over either the anterior (sustentaculum tali) or posterior (inferior to the medial talar tubercle) joint line depending on which is dysfunctional.

The adjacent figures show the thumb positions for an eversion manipulation (inversion subluxation) with the thumbs positioned on the sustentaculum tali.

The foot is lifted into eversion and then flicked downwards into eversion with pressure being applied by the thumbs at the end of the flick. This is an osteokinematic manipulation so the direction of the manipulation is always lateral regardless of whether the anterior or posterior joint is involved.

Inversion Manipulation (Eversion Subluxation)
To manipulate to gain inversion (an eversion subluxation), the patient lays so that the lateral border of the foot is uppermost. The therapist takes up the same position but now with the other leg. The thumbs are placed over the lateral border of the calcaneus. The posterior joint is found as the area just posterior and inferior to the lateral malleolus and the anterior being just posterior to the cuboid and just below and anterior to the malleolus. Again this is an osteokinematic manipulation so the thrust is always downwards that is into inversion.