Kirner’s deformity and hammertip are two completely different disorders: Pathogenesis: Kirner’s deformity is a developmental disorder of the terminal phalanges that results in curvature of the terminal phalanges; hammertip is a structurally normal development of the finger itself, which is caused by trauma resulting in extensor tendon rupture at the stops or avulsion fracture, and the terminal phalanges are unable to straighten and are bent and drooped. Appearance of the terminal segment of the finger: Kirner’s deformity has the terminal segment of the finger curved to the palmar and radial sides, and the terminal segment shows the signature hunchback hook deformity; the terminal segment of the finger in hammer finger is normal in development. Nail appearance: Kirner deformity nails are hooked; hammer finger nails are normal. Joint movement: Kirner deformity has normal and natural joint movement; the hammer finger is not actively straightened. Physical examination: the end joints of the fingers in Kirner deformity are inherently curved and therefore cannot be straightened; the hammer finger can be straightened.