Which bone is located on the medial side of the lower arm?

The ulna is the bone located on the medial side of the lower arm. It runs parallel to the radius, which is situated on the lateral side of the forearm. Anatomically, when a person is in the standard anatomical position (standing upright with palms facing forward), the ulna is positioned closer to the body compared to the radius.

The ulna is generally larger than the radius at the elbow joint and forms the dominant part of the forearm's bony structure on that side. It also plays a crucial role in forming the elbow joint in conjunction with the humerus. Understanding the positional relationships of these bones is essential for grasping human anatomy, particularly in contexts related to movement and function in the upper limb.