The cyma line is a radiological sign of the smooth joining of the midtarsal joint lines as a "lazy S-shape" of the talonavicular and calcaneocuboid joints on both AP and lateral views.
Disruption of the cyma line with anterior shift of the talonavicular joint can indicate true shortening of the calcaneus or rotation of the talus relative to the calcaneus as seen in pes planus . The cyma line can also be disrupted in a midtarsal (Chopart) injury .
History and etymology
A cyma line refers to the union of two curved lines in architecture and comes from the Greek word kyma meaning wave .