Purpose: We performed a biometric evaluation of the femoral trochlea in the human foetus and compared measurements with those observed in the adult in order to search for correlations with other biometric parameters of the human femur.

Material: Twenty-two foetuses with no orthopaedic anomalies were preserved in formol. The 44 knees were studied. Fœtal age varied from 26 to 40 weeks.

Method: After anatomic dissection, digital photographic documents were analysed using angular measurement software. The following dimensions were measured on the distal epiphysis: anteroposterior thickness of the condyles, protrusions of the lateral and medial trochleal edges, the difference in condyle height, the trochlear opening angle alpha, trochlear slope. Femoral anteversion, length of the femoral neck, and the neck-shaft angle were measured on the AP view of the femur.

Spearman’s test was used to search for correlations. Results were compared with those measured under the same conditions in a series of 32 adult knees published by Wanner.

Results: The alpha angle of trochlear opening was 148° with a coefficient of variability of 4%. The alpha angle was greater than 150° in 18 trochleae. The lateral edge of the trochlea was higher than the medial edge in 37/44 trochleae. There was no correlation by age and sex.

The femoral measurements showed 27.01° anteversion with very wide variability (coefficient 46%) and no correlation with trochlear opening.

No significant differences were observed between the fœtal and adult measurements.

Discussion: Our data are the first reporting anatomic measurements of the fœtal trochlea. The morphology of the lower extremity of the femur during the third trimester of pregnancy is globally the same as in adult femurs. Morphological changes of the proximal femur occurring during growth do not appear to modify the morphology of the distal femur. The deep and asymmetrical engagement of the patella onto the trochlea is a characteristic of modern man and is considered to be a consequence of bipedal stance. Our study would appear to confirm that the anatomic characteristics of the human trochlea have been integrated into the genome in the course of evolution. This suggests that a genetic origin of trochlea dysplasia, as suggested by Dejour, is a reasonable hypothesis.