Anatomy
Ossification of tarsal bones
- Calcaneus ossifies first, in fetal life, followed by the talus
- Cuboid ossifies around birth
- Lateral cuneiform ossifies at about 1 year
- Medial and intermediate cuneiforms ossify at about 2 to 3 years
- Navicular ossifies last, at about 3 years
- Late navicular ossification explains why dislocation is not visible in infant clubfoot radiographs
Physes and apophyses
- Metatarsals 2 to 5 have distal physes, the first metatarsal has a proximal physis
- Phalanges have proximal physes
- Calcaneal apophysis is the site of Sever disease
- Fifth metatarsal base apophysis lies parallel to the shaft, unlike a fracture line
- Distal tibial physis closes centrally, then medially, then laterally over about 18 months
- Asymmetric closure explains Tillaux and triplane fractures
Accessory ossicles
- Os trigonum, accessory navicular, os peroneum and os vesalianum
- Bipartite medial sesamoid can mimic fracture
Joints and arches
- Subtalar joint has anterior, middle and posterior facets
- Talocalcaneal coalition most often involves the middle facet
- Chopart joint is talonavicular and calcaneocuboid
- Lisfranc joint is tarsometatarsal, keyed by the recessed second metatarsal base
- Infant arch is masked by a plantar fat pad
- Medial longitudinal arch develops through the first decade
Radiographic angles
- AP talocalcaneal (Kite) angle about 20 to 40 degrees in children
- Parallel talus and calcaneus on AP and lateral views in clubfoot
- Lateral talar first metatarsal (Meary) angle near 0 degrees in a normal foot
- Calcaneal pitch increased in cavus and decreased in flatfoot
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.