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 66 of the 200 scored questions until 28 February 2027 and 72 from 1 March 2027. One foot contains 26 bones: 14 phalanges, 5 metatarsals and 7 tarsals.

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, while the medial malleolus and talus partly superimpose. 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 Bontrager's cast conversions add 5 to 7 kV for a small to medium plaster cast, 8 to 10 kV for a large plaster cast, or 3 to 4 kV for fiberglass. On AP stress views, a physician or other health professional holds or straps the foot and ankle, or the patient holds the position with long gauze looped around the ball of the foot (Bontrager).