Ulna- trochlear (semilunar) notch

Anterior view, right side

Anterolateral view, left side

The trochlear (semilunar) notch is an important landmark of the ulna because it is the articulating surface for the ulna of the humeroulnar joint that articulates with the trochlea of the humerus. This is a hinge joint allowing for flexion/extension. Dr. J recommends that you remember that the trochlea notch articulates with the trochlea, which makes it a Grant thing.