Roll - one bone rolling on another
Surfaces are incongruent
New points on one surface meet new points on the opposing surface
Rolling results in angular motion of the bone
Rolling is always in the same direction as the angulation bone motion
Rolling causes compression of the surfaces on the side to which the bone is angulating and separation on the other side
In normally function joints pure rolling does not occur alone but in combination with joint sliding and spinning.
Glide - One bone sliding across another
For a pure slide, the surfaces must be congruent, either flat or curved, therefore there is no pure sliding anatomically.
The same point on one surface comes into contact with new points on the opposing surface.
Direction of slide is dependent on whether the moving surface is convex or concave. (Convex-Concave rule)
Combined roll-sliding
The more congruent the joint surfaces are, the more sliding there is of one bony partner on the other with movement
The more incongruent the joint surfaces the more rolling
Muscles can actviely cause or control sliding movements of joint surfaces (rotatator cuff downward glide/ hamstring tibial posterior glide during flexion)
Spin — Rotation of a segment about a stationary mechanical axis
The same point on the moving surface creates an arc or a circle as the bone spins
Spining rarely occurs alone in joints but in combination with rolling and sliding.
Examples of spin include: shoulder flexion/extension, hip flexon/extension, and radiohumeral pronation/supination.