Ask a PT Response: "At the subtalar joint in non-weight bearing supination is the result of calcaneal inversion, plantarflexion and adduction. Pronation is the result of calcaneal eversion, dorsiflexion, and abduction.

 

At the subtalar joint in weight bearing supination is the result of calcaneal inversion, talar abduction and dorsiflexion. Pronation is the result of calcaneal eversion, talar adduction and plantarflexion.

 

When a patient undergoes an isolated subtalar fusion (arthrodesis) range of motion for both pronation and supination will be lost but not entirely as motion at the midtarsal joint can accomodate for these movements. Some studies have shown that an isolated subtalar joint arthrodesis limits talonavicular motion to about 26 percent and calcaneocuboid motion to about 56 percent. The percentage of restriction of motion obviously depends upon the position of the bones being fused. If the subtalar joint underwent fusion in supination, one would expect more restriction of the calcaneocuboid and talonavicular joints. Alternatively, if the subtalar joint underwent fusion in pronation, surgeons would expect more motion of the midtarsal complex (1). I hope this helps."