Structure of a Goniometer: Arms: It typically consists of two arms – a stationary (or “fixed”) arm and a movable (or “moving”) arm. Fulcrum: A pivot point or a small circular piece in the middle, where the two arms are attached. Scale: Surrounding the fulcrum, there’s a scale marked in degrees, which allows the user to measure the angle between the two arms. Usage: The stationary arm is aligned with a stable body part adjacent to the joint being measured. The movable arm is then aligned with the moving part of the limb. As the joint moves, the movable arm moves with it. The angle of the joint can be read from the scale where the movable arm points.