Congenital aplasia of the patella and the distal third of the quadriceps mechanism.

Congenital absence of the patella and aplasia of the muscles are very rare anomalies. We describe a 4-year-old boy with bilateral congenital aplasia of the patella and agenesis of the distal third of the quadriceps muscle who was unable to walk owing to the lack of active knee extension. The features of this child differed from all other conditions associated with patellar aplasia. The continuity of the quadriceps mechanism was restored and he began walking normally. This appears to be the first report of the combination of aplasia of the patella and the distal third of the quadriceps that was successfully treated.