The trochlea and capitulum are both located on the distal end of the humerus, which is the bone in your upper arm.

Here's how they relate to each other:

* Trochlea: The trochlea is a medial (towards the midline of the body) structure that articulates with the ulna (the bone on the pinky side of your forearm). It has a pulley-like shape, which helps with forearm rotation.

* Capitulum: The capitulum is a lateral (away from the midline) structure that articulates with the radius (the bone on the thumb side of your forearm). It is a rounded knob-like structure.

Therefore, the trochlea lies medial to the capitulum.