"肘的尺骨端" can be translated as "the ulnar end of the elbow" or more precisely, "the ulnar aspect of the elbow joint" (referring specifically to the part of the elbow related to the ulna bone).
Ulnar end/aspect: Indicates the part connected to or associated with the ulna bone (尺骨).
Elbow joint: The anatomical region where the humerus, radius, and ulna meet.
For clinical or anatomical contexts, "ulnar aspect of the elbow" is commonly used.