Final answer:
The proximal radio-ulnar joint is innervated by the ulnar nerve, which allows for pronation and supination movements of the forearm.
Step-by-step explanation:
The proximal radio-ulnar joint is innervated by the ulnar nerve. This joint is a uniaxial pivot joint that facilitates the movement of the radius during pronation and supination of the forearm, allowing the forearm and hand to turn over. This articulation is specifically between the head of the radius and the radial notch of the ulna. The ulnar nerve innervates many structures of the forearm and hand, providing both motor and sensory functions. The close relationship between the ulnar nerve and the ulnar collateral ligament on the medial side helps ensure the stability and proper function of the elbow and its associated joints.