What best describes angular motion of a joint?

What best describes angular motion of a joint?

• A. Turning a bone on its long axis
• B. Increase/decrease in the angle between two bones (flexion/extension, ab/adduction, lateral flexion, circumduction)
• C. Gliding motion of surfaces
• D. Elevation/Depression

Answer: (B)

Angular motion is movement that changes the angle between two bones at a joint. When a joint flexes or extends, the angle gets smaller or larger; abduction and adduction move limbs in ways that change that angle as the bones move away from or toward the midline; lateral flexion bends the trunk to the side, altering the joint angles; circumduction combines these actions to trace a circular path, all by changing the angle between the bones. Turning a bone on its long axis is rotation around the bone’s own axis, a motion about the bone rather than a change in the angle between two bones, so it isn’t described by angular motion in the joint-angle sense. Gliding moves are surface-to-surface slides with little to no change in the angle between bones, and elevation/depression are vertical shifts that don’t inherently alter the joint angles.

Angular motion is movement that changes the angle between two bones at a joint. When a joint flexes or extends, the angle gets smaller or larger; abduction and adduction move limbs in ways that change that angle as the bones move away from or toward the midline; lateral flexion bends the trunk to the side, altering the joint angles; circumduction combines these actions to trace a circular path, all by changing the angle between the bones.

Turning a bone on its long axis is rotation around the bone’s own axis, a motion about the bone rather than a change in the angle between two bones, so it isn’t described by angular motion in the joint-angle sense. Gliding moves are surface-to-surface slides with little to no change in the angle between bones, and elevation/depression are vertical shifts that don’t inherently alter the joint angles.