What is the proximal attachment of the pronator teres?

The proximal attachment of the pronator teres muscle is found at the medial epicondyle of the humerus. This location is significant because the pronator teres plays a vital role in forearm pronation and also acts as a flexor of the elbow. The medial epicondyle serves as a common attachment point for several muscles that are involved in flexion and pronation of the wrist and forearm, which emphasizes the importance of this region in upper limb function.

The muscle originates from this bony prominence and extends downward to attach to the radius. This anatomical relationship enables the muscle to effectively execute its actions during movement, underlining the functional importance of the medial epicondyle as the starting point for the muscle fibers of the pronator teres.

In contrast, the other options do not serve as the proximal attachment for this muscle. The coronoid process of the ulna is another attachment site for different muscles, while the base of the 2nd metacarpal and the flexor retinaculum are not related to the pronator teres's proximal attachment. Thus, the medial epicondyle of the humerus is appropriately recognized as the correct and relevant attachment point for the pronator teres.