Knee deformities in multiple hereditary exostoses. A longitudinal radiographic study.

For a mean period of 7.8 years, the morphology of knee deformity and its annual changes in 8 patients (16 knees; mean age at the initial examination, 8.4 years) with multiple hereditary exostoses were evaluated radiographically. Knee deformity developed during the growth spurt period. Genu valgum with a femorotibial angle that decreased more than 2 standard deviations from the mean of age-matched normal children was observed in 6 of the 16 knees. In 3 of these 6 knees, recurrent dislocation of the patella was observed. Angulation of the femur varied among the knees, but the tibia showed valgus angulation in the proximal metaphysis in all knees. Thus, knee deformity in patients with multiple hereditary exostoses was primarily genu valgum caused by valgus angulation of the tibia.