Measurement · RAMUS
Ramus height (Ar–Go)
Loading the reference ceph.
Definition
The length of the mandibular ramus from Articulare to Gonion.
How
Measure Ar→Go in mm (norm ≈ 44 mm adult; age-dependent).
Purpose
Ramus height is the main engine of posterior face height: a short ramus cannot 'keep up' with molar eruption, rotating the mandible open (high-angle open-bite pattern); a tall ramus closes the bite forward. Also a growth-watch metric in asymmetries.
High
Above the norm reads as a tall ramus — posterior face height favors forward/horizontal rotation (deep-bite tendency).
Low
Below the norm reads as a short ramus — deficient posterior face height, clockwise rotation, open-bite/high-angle risk.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Ramus height (Ar–Go) here is a real reading and not a diagram.