1. Lateral impaction injuries of the tibial plafond generally are of two types: subchondral compression fractures and superiorly displaced or impacted fragments, usually a part of either a posterior malleolar fragment or, less often, an anterior margin fragment.

2. Unrecognized compression fractures of the lateral plafond occur most commonly in severe trimalleolar fractures with dislocation of the ankle joint.

3. Fractures of the posterior or anterior margin usually involve the lateral tibial plafond and often involve a larger weight-bearing area than suspected.

4. Anteroposterior and lateral roentgenograms usually do not reveal the extent of injury to tue lateral plafond and oblique roentgenograms may be necessary.

5. A follow-up study of twenty-five of thirty-six patients with bimalleolar or trimalleolar fracture-dislocations of the ankle that came to arthorodesis over a ten-year period on a large orthopaedic teaching service revealed that a fracture of the lateral plafond of the tibia was a major contributing factor in thirteen patients.

6. Closed anatomical replacement of displaced or impacted large articular fragments is recommended if possible, and, if not, open reduction. Subcortical wedge osteotomy and bone-grafting of the lateral plafond is described for subcortical compression fractures in a preliminary report; however, the follow-up is too brief for results to be of significance.