Osteokinematics VS. Arthrokinematics

We use OSTEOKINEMATIC terms, such as abduction or adduction, flexion or extension, to name the movements that occur between bones at synovial joints. These terms describe the movements that occur around a center of rotation, namely the joint axis.

We speak as if this joint axis is a fixed point, as if the center of rotation is stationary like an automobile axle. Joint axes' locations are fairly stable, but only because the joint surfaces move in a very specific way.

ARTHROKINEMATICS is the general term for the specific movements of joint surfaces. Normal joint surface movement is necessary to ensure long-term joint integrity. (Joint surface movements are sometimes called joint play motions or component motions).

Joint surfaces move with respect to one another by simultaneously (1) rolling, (2) gliding, and (3) spinning. This discussion focuses on how joint surfaces roll and glide with respect to one another, and largely ignores the spin component.





http://moon.ouhsc.edu/dthompso/namics/arthkin.htm