In supination, how are the radius and ulna positioned?

In the anatomical position of supination, the radius and ulna are parallel to each other, with the radius positioned laterally to the ulna. This position is significant for several functions in the upper limb, particularly when the forearm is rotated so that the palm of the hand faces upward or forward. Supination is commonly observed when you hold your hand out to receive something, such as a drink.

The parallel alignment allows for optimal functionality, as it provides stability and proper leverage for the muscles operating in this position. In contrast, when the radius crosses over the ulna during pronation (the opposite motion), the functional dynamics of the forearm and wrist differ significantly, impacting movement and grip strength. Recognizing the correct positioning of the radius and ulna in supination is essential for understanding wrist and arm mechanics in human anatomy.