Congenital dislocation of the patella.

In 8 congenital patellar dislocations, in 7 patients, the patella was permanently and laterally dislocated, and irreducible or difficult to reduce. The patella usually was hypoplastic and showed absent facets. The intercondylar groove of the femur also was underdeveloped. In all but one patient, knee function was improved by a surgical procudure which involved lateral release of ptella, medial transpositon of patellar tendon, and plication of medial capsule or advancement of vastus medialis.