Early intrauterine presence of congenital dislocation of the knee.

We report the histologic findings of congenital dislocation of both knees of a 19.5-week-old spontaneously aborted fetus. Grossly and histologically, both knees were grade II congenital dislocations (subluxation), which are characterized by hyperextension of the knee with rotatory subluxation. Comparing the morphologic changes to age-matched normal controls allowed us to distinguish between primary and secondary changes. The most impressive fetal abnormalities were partial fibrosis of the quadriceps, absence of a suprapatellar pouch and incomplete patellofemoral joint cavitation. The presence of these findings suggests that they most likely cause, and do not result from, dislocation. This specimen is the first preterm fetus to be described with the features of congenital dislocation of the knee of any type.