Patellar instability can significantly influence the locomotor function in children with Down’s syndrome. The aim of this study was to evaluate the mid-term results of the operative treatment of patellar instability in children with Down’s syndrome. The study included eight children (10 operated knees) with Down’s syndrome and associated patellar instability. The children’s age ranged from 6 to 11 years (the mean age was 7 years 9 months). The operative treatment involved Green’s quadricepsplasty in six cases (eight knees) and Green’s quadricepsplasty augmented with a modified Galeazzi procedure – semitendinosus tenodesis – in two cases. The mean follow-up period was 3 years and 3 months. We achieved a stabilization of the patellofemoral joint and a correction of the position of the patella in seven knees (five of these were treated with Green’s procedure and in two cases Green quadricepsplasty was combined with the Galeazzi procedure). We did not observe any recurrence of patellar dislocation in this group during the follow-up period. We noted two failures, defined as a recurrence of dislocation, during the mean of 9 months postoperatively. Green’s quadricepsplasty provides satisfactory results in younger children with Down’s syndrome. In older children, we recommend the modified Galeazzi procedure.