Arthroscopic study of the knee joint in fetuses

The purpose of this study was to macroscopically examine the fetal knee joint via arthroscopy. We have attempted to identify and describe the specific characteristics of the fetal knee joint, how it evolves during the last few weeks of intrauterine development, and any possible variations with regard to the adult knee.

Observational anatomic case series.

We used 20 frozen fetuses with a gestational age of 24 to 40 +/- 2 weeks, obtained from spontaneous abortions. Examination was performed with standard arthroscopic surgical equipment, using a 2.7-mm optical lens. Whenever possible, we tried to use standard arthroscopic portals. Images were obtained for comparison with the adult knee.

Suprapatellar and infrapatellar septa were an almost consistent finding. The suprapatellar septum always opened laterally and was intact in the developmentally younger specimens. We found 2 mediopatellar septa. The femoral attachment of the anterior cruciate ligament (ACL) differed in appearance from that of the adult in that it was more ribbon-like. The lateral meniscus had a more spread-out appearance than its adult counterpart, especially in the specimens of a younger gestational age. We were surprised at the easy accessibility of the popliteal hiatus and the clear arthroscopic vision we were able to obtain of the involved structures.

To our knowledge, this is the first arthroscopic study to target the fetal knee. The results indicate minimal differences when compared with the adult knee, and for some structures, such as the popliteal hiatus, the anatomy seen was easier to discern than in adult knee arthroscopy.