Is it safe to associate an everted calcaneus with an everted subtalar joint all the time in a closed kinematic chain? For example in pes planus? Also, is it safe to always associate an inverted calcaneus with an inverted subtalar joint in a closed chain?

By accepted anatomical conventions, eversion is not a movement normally associated with the Talus. A more appropriate description of the movement of the talus would be abduction or adduction depending on the position of the calcaneus in closed chain. For example when considering foot pronation, calcaneal valgum (calcaneal eversion) results in movement of the talus into adduction and plantarflexion relative to the calcaneus. As the talus moves in the transverse plane into adduction the leg follows resulting in internal rotation. Also, as the talus plantarflexes it moves the knee into slight flexion.

In the case of foot supination, calcaneal varum (calcaneal inversion) results in movement of the talus into abduction and dorsiflexion relative to the calcaneus. As a result of the transverse motion of abduction by the talus the leg follows with external rotation. Also, talar dorsiflexion in the sagittal plane creates slight motion at the knee into extension.

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