Foot, Ankle & Calcaneus Positioning for the ARRT Exam

Overview

Foot, Ankle and Calcaneus covers everything at or below the ankle joint: toes, foot, sesamoids, calcaneus and the ankle itself. It sits inside the ARRT Procedures domain, worth 72 of the 200 scored questions. One foot contains 26 bones: 14 phalanges, 5 metatarsals and 7 tarsals, and the seven tarsals supply nearly every landmark and centering point in the region.

The most tested distinction is the spread of frontal ankle rotations. The AP ankle is taken at 0 degrees, the AP mortise at 15 to 20 degrees of internal rotation, and the AP oblique at 45 degrees. The small rotation opens the entire mortise, with an even 3 to 4 mm space over the talar surface, while the 45 degree oblique opens the distal tibiofibular joint and closes the medial mortise. Four more angles carry marks: 10 degrees posteriorly on the AP foot, 10 to 15 degrees on the AP toes, 15 degrees on the weight-bearing AP foot and 40 degrees cephalad on the plantodorsal axial calcaneus.

Centering repeats: the base of the third metatarsal serves the AP and oblique foot, a point midway between the malleoli serves four of the five ankle projections, and the lateral calcaneus centers 1 inch below the medial malleolus. Rotation checks are single landmarks: the distal fibula over the posterior half of the tibia on any lateral, and the sustentaculum tali in profile on the axial calcaneus.

A Lisfranc injury needs weight-bearing AP and lateral views plus a 30 degree medial oblique, gout classically strikes the first MTP joint, and cast conversions add 5 to 10 kV for plaster or 3 to 4 kV for fiberglass. On AP stress views, a physician or other health professional holds the stress, never the radiographer.