The forearm bones are four bones that make up the arm between the elbow and the wrist. The two bones on the medial side of the arm are the ulnae, which are also known as the ulnas. On the lateral side of the arm are the RADII, which are slightly shorter than the ulnae. The humeri are the bones that connect the shoulder to the elbow. All four of these bones work together to provide stability and movement to the arm.