Figure 2.11 cont’d (B) Biaxial joints move in two planes around two axes. (C) Triaxial joints move in three planes around three axes.
movement is discussed further in the following arthro- kinematics section and in each chapter related to specifi c joints. The humeroulnar joint is an example of a hinge joint, as it fl exes to bring the hand toward the mouth and extends to reach toward an object. As the elbow fl exes and extends, it moves through the sagittal plane around a frontal axis.
Another type of uniaxial joint is a pivot joint, where one bone spins around a single axis of rotation. This type of joint functions similar to a doorknob, as one ring-shaped surface rotates around a surface within the ring. An example of a pivot joint is the atlantoaxial joint in the cervical spine. The atlas (C1) rotates around the axis (C2). More than 50% of the rotation that occurs
