Thirty-eight cases of Larsen's syndrome were analyzed with an average follow-up of 13 years. Knee deformities were classified according to Leveuf and Pais grades: 12 patients had a grade 1 tibiofemoral dislocation, five had a grade two, and 18 had a grade 3. Six patients had isolated dislocations or subluxations of the patella. Fourteen patients with 22 unstable knees were surgically treated. This series supports the idea of early treatment of knee problems, with an open procedure for grade 3 (resection of medial and lateral retinacula and iliotibial fascia, V-Y reconstruction of the extensor apparatus, suture of the medial plane, medial transfer of one-third of the patellar tendon, capsuloraphy, tibiofemoral pinning, and plaster cast). Performing surgery on grade 2 dislocations is worthwhile only when they are accompanied by patellofemoral dislocations. If they are grade 1, progressive casting in flexion is justified. Patellofemoral dislocations should be operated on early. Dislocatable patellas should be treated only if they interfere with function.