Concept and its Application in Body Movements

A movement is usually referred to by the single plane in which it mainly occurs — for example, walking is described as a sagittal-plane movement. In reality, that only describes the gross direction of the movement. At the level of an individual joint, movement occurs in all three planes, not just one.

Tri-planar motion

Take walking (gait). During a single stride the hip is:

• flexing and extending in the sagittal plane,
• adducting and abducting in the frontal plane, and
• rotating internally and externally in the transverse plane.

The same is true of every joint of the lower limb. What you actually see (the obvious sagittal-plane swing of the hip) does not show the eccentric force absorption and concentric force production going on in all three planes at once — the hip quietly decelerates internal rotation and adduction while accelerating external rotation and abduction. This simultaneous, three-component movement is called tri-planar motion, and all functional movements are three-dimensional in this way.

Even so, a single-plane description remains the most useful way to generalise gross movement patterns — which is why we still speak of a movement's dominant plane, motion and axis: