PURPOSE: Untreated meniscus injuries accompanied with fractures of lateral tibial condyle may cause prolonged pain and post-traumatic arthritis. Lateral displacement of fractured fragment of lateral tibial condyle was found to be related to the incidence of lateral meniscus tear. We established the risk groups for lateral meniscus injuries on the basis of the degree of the lateral displacement of lateral tibial condyle. MATERIALS and METHODS: Risk groups for lateral meniscus injury in fractures of lateral tibial condyle were evaluated in 39 knees, retrospectively, using plain roentgenograms and arthroscopic findings. On the knee anteroposterior radiography, displacement of lateral tibia condyle were classified into three groups according to the probability of lateral meniscus INJURY: high risk group for above 8mm of lateral displacement; moderate risk group for 4- 8mm; low risk group for less than 4mm. RESULTS: High risk group has ten meniscus injuries among 13 knees(76.9%) and moderate risk group had the seven meniscus injuries of 18 knees(38.9%). Low risk group of eight knees had no meniscus injury(0%). These different incidences among groups were statistically significant(p<0.05). CONCLUSIONS: The authors suggest that the incidence of lateral meniscus injury was related to the degree of lateral displacement of lateral tibial condyle, and our definition of risk groups are useful for prediction of lateral meniscus injury in fracture of lateral tibial condyle.