Table 1: Radiographic classification of transchondral fractures of the talus.

Stage Definition
I Compression fracture with intact overlying cartilage
II Incomplete avulsion of an osteochondral fragment
III Complete avulsion of an osteochondral fragment without displacement
IV Avulsed fragment displaced into joint

Berndt AL, Harty M. Transchondral fractures (osteochondritis dissecans) of the talus. J Bone Joint Surg Am. 1959;41-A:988-1020.