The term ARM STIFFENER can be broken down into two parts: the ULNA, which is a 4-letter word, and the stiffener. The ULNA is one of the two bones in the forearm, located on the medial side of the arm. It is the larger of the two bones and is responsible for the movement of the wrist and elbow. The stiffener is a device that is used to support and stabilize the arm. It is typically used to help reduce pain and discomfort caused by arthritis or other conditions that affect the arm.