None of the oblique ligaments have a known function.

An oblique ligament holds the hinge.

Anterior oblique ligament (AOL)

The anterior oblique ligament (AOL) attaches from the undersurface of the medial epicondyle to the medial ulnar surface slightly below the coronoid process.

In extension, the oblique ligament prevents passive DIP flexion and PIP hyperextension as it tightens and pulls the terminal extensor tendon proximally.

In the case of the Bennett's fracture, the proximal metacarpal fragment remains attached to the anterior oblique ligament, which in turn is attached to the tubercle of the trapezium bone of the CMC joint.