Reference lines/Foot axes:
a) Anterior posterior view:
Rearfoot longitudinal axis:
Formed by a line that bisects the posterior aspect of calcaneus and continues anteriorly to the anterior medial edge of the calcaneus. Often the posterior aspect of the calcaneus is not visible, so a line parallel to the anterior lateral edge of the calcaneus is usually used.
Lessor tarsus longitudinal axis:
Line is drawn from medial distal aspect of medial cuneiform to medial proximal aspect of navicular – this line is bisected in centre. Another line is drawn from lateral distal aspect of cuboid to lateral proximal aspect of cuboid – this line is bisected in centre. Theses two bisections are then joined – line at right angles to this line is the lessor tarsus axis.
Metatarsus longitudinal axis:
Formed by a longitudinal bisection of the shaft of the second metatarsal.
b) Lateral view:
Plane of support:
Formed by a line joining the plantar most aspect of the plantar calcaneal tuberosity to the most plantar aspect of the head of the fifth metatarsal.
Calcaneal inclination axis:
Formed by a line joining the most plantar aspect of the calcaneal tuberosity and the most distal plantar aspect of the calcaneus.
Talar axis/collum tali axis:
Formed by a line joining the bisection of the most distal and proximal aspects of the neck of the talus.
First metatarsal axis:
Formed by a bisection of the shaft of the first metatarsal. Care needs to be taken not to bisect the base or head of the first metatarsal.