We report results of surgical treatment of ten knees affected by patellar dislocation in six children with Down syndrome. Four knees showed a dislocatable patella (grade III according to Dugdale), two a dislocated reducible patella (grade IV) and four a dislocated irreducible patella (grade V). Symptoms included frequent falls, limping and pain. In all the cases a Roux-Goldthwait-Campbell procedure was performed. Mean age at surgery was 10 years (range 6 years and 6 months to 13 years and 4 months). Patients were reviewed at an average follow-up of 8 years and 8 months (range 3 years and 6 months to 11 years and 5 months). None showed signs of recurrence of the dislocation. The median Lysholm score improved from 57.5 to 91/100. Statistical analysis showed a significant effectiveness of the procedure in improving function, and that surgery was significantly more effective in patients with more severe disability.