The prenatal ontogenesis of human patellar ligaments

The etiology of diseases of the knee joint is currently associated with dysplastic disorders that develop already in prenatal ontogenesis. The purpose of the study is to identify the features of differentiation of the histological structure, differences in points of fixation and direction of fibers of the patellar ligaments in the prenatal period of human development. The research materials included histological sections of the knee joints of 20 embryos and fetuses of both sexes aged from 6 to 38 weeks, stained with hematoxylin and eosin and Van Gieson. The study revealed the features of differentiation of cellular composition, the timing of the formation of collagen fibers of various types at different stages of prenatal ontogenesis and the two-layer structure of the medial and lateral suspensory ligaments, the patellar ligament, interconnected by solitary fibers. The stages of development of the anatomical structures of the ligamentous apparatus of the knee joint have been determined. The given structural features of the patellar ligaments allow us to assert the formation in the human fetus of a single morphological complex “quadriceps femoris tendon - patella”. The data obtained also suggest that the patella in the human fetus has a stronger fixation on the medial side than on the lateral side due to the tendon bundles of the vastus medialis muscle and the patellar ligament. By the time of birth, the patella and derivatives of the tendons of the quadriceps femoris muscle represent a single morphological complex of the knee joint. Between the superficial and deep layers of the patellar ligament there are solitary bundles of collagen fibers, passing from one layer to another, providing strength on the one hand, and synchronicity in the development of ligament functions on the other. This is precisely what can explain the deviation of the apex of the patella at the time of birth from the long axis of the femur to the medial side, causing the valgus position of the lower limb in newborns. The results of the study may have practical significance in improving the diagnosis and surgical treatment of developmental disorders of the musculoskeletal system in pediatric orthopedics and traumatology.