Final answer:
The elbow joint is stabilized by the ulnar collateral ligament medially, the radial collateral ligament laterally, and the annular ligament, which supports the head of the radius at the proximal radioulnar joint.
Step-by-step explanation:
The main ligaments that stabilize the elbow joint include the ulnar collateral ligament on the medial side and the radial collateral ligament on the lateral side. The ulnar collateral ligament originates from the medial epicondyle of the humerus and attaches to the proximal ulna, effectively resisting hyperextension of the elbow. The radial collateral ligament arises from the lateral epicondyle of the humerus and merges with the annular ligament, which encircles the head of the radius at the proximal radioulnar joint, a pivotal area for rotation during pronation and supination of the forearm.