The authors performed a biometric analysis of the femoral patellar groove in fetus and compared their findings with those observed in adults. Forty-four formalin-preserved fetuses were studied (13-38 weeks). Digitalized images were used to obtain measurements (alpha angle of the groove, trochlear slopes thetaL and thetaM). A comparison of means of independent samples between our series and adults was performed. For each angle of the distal epiphysis (alpha, thetaL, thetaM) there was no significant difference between this fetal series and adults. This is the first biometry of the fetal patellar groove. The morphology of the lower femur appears to be the same in fetus and adults. The results of this study suggest that the anatomic characteristics of the patellar groove could have been integrated into the genome during the course of evolution. This would be in favor of a genetic origin of patellar groove dysplasia.