The ulna of the forearm is located on the inner side of the forearm and can be located and touched by the patient in two simple ways: 1. The patient should first locate the calcaneus and then follow the calcaneus gradually upwards. After passing the wrist joint, the bone touched is the ulna. The ulna is a long bone that runs parallel to the long axis of the forearm and leads upward to the elbow joint. 2. The patient can flex and extend the elbow and feel the most prominent part of the elbow joint, which is the tip of the elbow. At the tip of the elbow, gradually follow the skin down to touch, can feel a long strip of bone, this bone is the ulna. The ulna is a very important structure for the forearm, as it is connected to the radius on the other side through the interosseous membrane and interosseous muscle, so that the forearm can fulfill its weight-bearing and weight-carrying functions. In addition, because the ulna is so hard, it is often used by the body as a protection for itself and as a support for the body when crawling.