The mechanism of injury is commonly a fall on the outstretched hand with the elbow extended, with the force applied indirectly to the distal humerus ... and the medial epicondylar epiphyseal ...

Type 1 Medial head of the triceps remains posterior to the medial epicondyle with passive elbow flexion. Type 2 Triceps subluxates onto but not anterior to the medial epicondyle with elbow flexion.