Pronation rotates the forearm so the palm faces posteriorly from the anatomical position, whereas supination rotates it so the palm faces anteriorly. With the elbow flexed, these positions are commonly described as palm down and palm up, respectively.
The Reasoning and Mechanism
In the anatomical position, the body is upright with the arms by the sides and the palms facing forwards. Pronation and supination occur at the proximal and distal radioulnar joints, around the forearm's longitudinal axis.
During pronation, the radius rotates across the relatively stationary ulna. During supination, the radius returns to a parallel position alongside the ulna. These movements occur in the transverse plane around a longitudinal axis.
| Feature | Pronation | Supination |
|---|---|---|
| Palm from anatomical position | Faces posteriorly | Faces anteriorly |
| Palm when elbow is flexed | Faces downwards | Faces upwards |
| Radius and ulna | Radius crosses over ulna | Bones are approximately parallel |
| Sporting example | Turning the palm down during a table-tennis forehand | Holding the palm up when catching a ball underarm |
The terms can also describe movements of the foot, but their meanings are more complex there. Foot pronation combines eversion, abduction, and dorsiflexion, while foot supination combines inversion, adduction, and plantar flexion. In an IB question, identify whether the movement concerns the forearm or foot before answering.
A common misconception is that pronation always means “palm down” and supination always means “palm up.” Those descriptions apply when the elbow is flexed; using anterior and posterior relative to the anatomical position is more precise.
Exam Technique
For an IB SEHS question using the command term distinguish, state both opposing movements and make the difference explicit. Refer to palm orientation and the relationship between the radius and ulna; for an applied question, identify the movement at a specified phase of the sporting action.