Gonion: the Jaw Angle Point in Facial Analysis
Quick facts
- Definition
- A reference point at the vertex of the angle of the mandible, between the ramus and the body.
- Abbreviation
- Go, in cephalometric tracings.
- Use
- It enters measurements such as the gonial angle and mandibular planes.
- Difference from the mandibular angle
- The angle is the structure you see and feel; the gonion is the point marked on it for measuring.
The gonion is a measurement point. It sits at the vertex of the angle of the mandible, where the vertical ramus meets the horizontal body. In cephalometry tracings it appears with the abbreviation Go. Anyone assessing the lower contour of the face will come across the term in books, reports and articles.
What is the difference between the gonion and the mandibular angle?
The mandibular angle is the structure you can see and feel on the face: the "corner" of the jaw. The gonion is the point chosen to represent that corner in a drawing or an X-ray. One is anatomy, the other is a measurement landmark.
Where is the gonion used?
In the analysis of the lower third, the gonion is combined with other points, such as the pogonion, to calculate:
- the gonial angle, which describes how open or closed the mandible is;
- the length of the mandibular body, from the gonion to the chin;
- mandibular planes used in reading facial proportion.
These measurements help you understand the jawline and the shape of the face, but they do not decide the plan on their own. Clinical assessment, palpation and the patient's preferences remain central.
Frequently asked questions
What is the gonion in facial analysis?
It is the point at the vertex of the angle of the mandible, used as a measurement landmark. It is the basis for calculating the gonial angle and other relations of the lower third.