Cyma line

The Cyma line is a sign seen on a radiograph that appears as a ‘lazy’ S shape formed by the midtarsal articulations of the talonavicular and calcaneocuboid joints – the Cyma line should appear smooth and unbroken in a well-aligned foot.

cyma line

Lateral (A) and Dorsiplantar (B) of the Midtarsal joint Cyma line (From Gamble & Yale (1975)

‘Cyma’ comes from the Greek word ‘kyma’ that means a wave or a wavy molding. The term is used in architecture where the molding of a cornice is wavelike in form and the outline consists of a concave and a convex line. An S-shaped curve is formed by the union of those concave and convex lines:
cyma architecture

‘Breaks” in the continuity can occur in the Cyma line with pronation and supination of the foot. With a pronated foot the Cyma line breaks anteriorly due to anterior movement of the talus on the calcaneus. In a supinated foot, the Cyma line may be broken posteriorly.

cyma line break

An anterior break in the Cyma line with a pronated foot. (From Gamble & Yale (1975)

Related Pages:
Relationship Between Bones / Radiographic Charting

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