The humerus is the long bone that runs from the shoulder to the elbow, and the ulna and radius are the two bones that make up the forearm.[6] The capitellum is the rounded knob on the end of the humerus and it is held by the radius due to the radius's cup-like shape. Panner Disease is part of a family of bone development diseases known as osteochondrosis.[6][7] In osteochondrosis, the blood supply to an area of developing bone in the dominant elbow is temporarily disrupted by something that is not yet well understood.[6] Therefore, the tissues in the bone are not getting enough blood and they begin to go through necrosis, and they begin to die. Normally, bones grow by the expansion and uniting of the growth plates, but osteochondrosis disrupts this process and the result is cell death and the loss of newly formed tissue.