Progressive Genu Valgum Resulting From Idiopathic Lateral Distal Femoral Physeal Growth Suppression in Adolescents

Background: Progressive genu varum with disturbance of medial tibial physeal growth (classic Blount disease) is a well-studied phenomenon, and in rare cases, genu varum can occur because of medial distal femoral physeal growth disturbance (so-called femoral Blount disease). To our knowledge, progressive genu valgum caused by disturbance of lateral distal femoral physeal growth has not been described. Methods: This article presents the history, clinical findings, imaging studies, results of surgical treatment, and speculation regarding the etiology of this disorder in 2 girls. Results: Both patients were overweight girls without a history of injury or prior medical disorder who presented with relatively rapid progression of knock-kneed deformity. Magnetic resonance imaging studies demonstrated unusual circular peglike disturbances of the lateral distal femoral physes. Treatments in both cases included corrective distal femoral osteotomy and epiphysiodesis to prevent further deformity. Conclusions: Obesity and repetitive microtrauma, superimposed on genetic factors (physis that is sensitive to compressive forces), may contribute to the etiology of this rare disorder. Level of Evidence: Therapeutic, level IV.