Passing circuitously across the forearm, the pronator connects the humerus’ centre epicondyle to the medial side of the ulna’s coronoid process. At the ulna, the pronator resembles a thin fasciculus, while the humeral head lies closer to the skin and is much larger. From time to time, the ulnar head can be missing and occasionally, there are slips from each of the biceps brachii, the brachialis, and the medial intermuscular septum. The lateral border of the pronator forms the centre boundary of the trilateral impression known as the cubital fossa, positioned just in front of the elbow.
True to its name, the pronator pronates the forearm, which really just means twisting it so the palm faces different directions (depending on the angle of elbow flex). Innervation (control) comes from the median nerve.