Goniometry is the measurement of the angle formed at a joint. It is commonly used to assess range of motion, compare movement between sides of the body, and document change over time.
A traditional goniometer has two arms aligned with body segments and an axis positioned over the joint. Digital tools can apply the same principle to an image or video by placing points or lines along visible anatomical landmarks.
Common Uses
- Measuring active or passive range of motion
- Comparing joint positions at different phases of a movement
- Tracking changes during rehabilitation or training
- Providing objective visual feedback
Reliable goniometry depends on consistent landmark placement, camera position, and measurement technique. In 2D video analysis, the camera should be positioned as close as practical to perpendicular to the plane of motion. A poor viewing angle can introduce perspective error and make an apparent joint angle differ from the movement occurring in three-dimensional space.
Video-based goniometry is useful for repeatable observation and comparison, but its accuracy depends on image quality and setup. It should not be treated as a medical diagnosis on its own.