Congenital dislocation of the patella. Part I: pathologic anatomy.

There has been considerable confusion between true congenital dislocation of the patella and other patellar instabilities. Only very few papers describing the anatomical features of congenital dislocation of the patella are found in the literature. The purpose of this paper was to describe the anatomical anomalies found in two cadaver specimens of a true permanent and irreducible congenital patellar dislocation. The quadriceps femoris is short and displaced laterally and acts as a knee flexor. The patella is small, articulating with the outer aspect of the lateral condyle, with no possibility of medial reduction onto the trochlea. Many other anomalies involving the bones, muscles, and nervous structures were found. Congenital dislocation of the patella must be distinguished from other patellar dislocations in children. The severity of structural anomalies is mainly owing to its prenatal onset. Congenital