A protruding elbow bone is usually a protrusion of the ulnar eminence or the internal and external epicondyles of the humerus. The most common cause of this condition is a fracture of the outer epicondyle of the humerus, the ulnar eminence, or the radial tuberosity of the elbow joint due to a traumatic injury sustained in youth or infancy, which is not treated properly and results in a deformed healing of the fracture. This is a common clinical condition. After the deformity heals, it is often overlooked because there is no obvious local pain, resulting in a localized bony protrusion in adults. However, there are usually no obvious clinical symptoms and the most common is that the elbow joint flexion and extension may be limited, but it does not affect normal life and physical work.