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This is an illustration that depicts the cardinal plane movements of the lower extremity. This is a biomechanical demonstration of the functional orthopedic nature of podiatry

In the anatomical lower extremity, there exist three cardinal planes: Sagittal, Frontal, & Transverse. Anatomical motion that occur parallel to these planes are considered to be the dominate motions of that plane.
 
The Horizontal, or Transverse, plane divides the foot in a superior and inferior half.  Adduction and Abduction are the motion that occur.  Parallel to this plane, adduction is when the foot and leg are medially rotated towards the midline of the body, and Abduction is when the foot and leg are laterally rotated away from the midline.
 
The Frontal, or Coronal, plane divides the foot in to Anterior and Posterior portions.  Inversion and Eversion are the motions that occur parallel in this plane.  Inversion is when the plantar surface of the foot rotates toward the midline of the body and Eversion is then the plantar surface of the foot rotates away from the midline of the body.
 
The Sagittal plane, which in the foot is approximated to the osteological axis of the 2nd metatarsal, separates the foot in to medial and lateral halves.  Parallel to this plane, Dorsiflexion and Plantarflexion refer to the relationship between the surface of the foot and the anterior surface of the leg.

Thus dorsiflexion is when the dorsum of the foot moves toward the leg whereas plantarflexion is defined when the dorsal surface of the foot  moves away from the leg.  It should be noted that process of the walking happens in the sagittal plane.
 
Triplaner motions does not occur in parallel to any of the three cardinal body planes mentioned. It is merely ONE motion consisting of components from all three body planes.  This can be demonstrated in the lower extremity by the actions of Pronation and Supination  which are triplaner motions.
 
Pronation is a motion of the foot which is comprised of eversion, dorsiflexion, and abduction. With this, the foot is seen  to move toward the anterior leg while the toes and plantar surface moving away from the midline.
 
Whereas supination consists of inversion, plantarflexion, and adduction, resulting in the foot to move away from the anterior leg and with the toes and plantar surface moving toward the midline.
 
At a particular joint, in order for a given triplaner motion to be in supination or pronations it must consist of the motions disgust above.  The amount of each movement depends of the anatomy of the joint.  With that said it is critical to understand that pronation and supination are triplanar motions, but not all triplanar motions are considered pronation or supination.