The unstable patella in children.

The authors reviewed 102 unstable patellas which had been observed and treated from 1964 to 1990. They were divided according to whether they suffered from traumatic dislocations, recurrent dislocations or malformative instability. The clinical findings were the major stage of the check up. In the field of imaging, standard X-rays had to be performed in all cases. MRI was of interest in the congenital dislocations, in order to thoroughly investigate the soft tissue anomalies. Two types were described: Type 1 was observed in children with joint laxity, but without major X-ray anomalies; Type 2, a major femoropatellar dysplasia could be formed with some bone deformity. The latter was observed in the malformative instability. Four different surgical procedures have been used, from the release of the retinacula of patella to the medial displacement of the patellar tendon or the tibial tuberosity. This study emphasises the concept of a true development dysplasia of patella (DDP) which can gather the different varieties of the instability of patella.