The |ulna| is one of the two long bones (the other is the |radius|) which form the lower arm (forearm). The |ulna| articulates at each end with the ends of the |radius|, with the |humerus| at the elbow, and some of the |carpal bones| at the wrist. When the hand is turned with the palm facing up (called ~supination~), the |ulna| is on the medial (little finger) side of the forearm. When the hand is placed with the palm down (called ~pronation~), the |radius| crosses over the |ulna| in mid-forearm.
