Anterolateral Ligament of the Fetal Knee: An Anatomic and Histological Study.
The anterolateral ligament (ALL) of the knee has recently been described in detail. Most studies of the ALL have been conducted in adults; therefore, little is known about the anatomy and histology of the ALL in younger patients, and nothing is known about the fetal presence of the ALL.



To evaluate the ALL in human fetuses to determine its presence or absence and to describe its microscopic anatomy and histological features compared with the findings of studies conducted in adults.



Descriptive laboratory study.



Twenty human fetal cadaveric specimens were used. The mean age of the fetuses was 28.64 ± 3.20 weeks. The ALL was dissected in the anterolateral region of the knee, and its anatomic parameters, including its origin, insertion, and path in relation to known adjacent anatomic landmarks, in addition to its length, width, and thickness over the path toward the tibia, were measured. After dissection, the ALL was removed en bloc with a portion of the lateral meniscus for histological analysis of 4-μm sections, hematoxylin and eosin staining, and immunohistochemical staining for type I collagen.



The ALL was located in all dissected knees. Its origin was located at a mean distance of 1.87 mm from the origin of the lateral collateral ligament, with variations from the center of the lateral epicondyle to posterior and proximal to it, and it exhibited an anterior-inferior path toward the tibia, an insertion in the lateral meniscus approximately 2.08 mm anterior to the popliteal tendon, and another insertion in the tibia between the Gerdy tubercle and the fibular head at 2.46 mm below the articular cartilage. The histological sections of the ALL showed well-organized, dense collagenous tissue fibers with elongated fibroblasts (mean, 1631 fibroblasts/mm2) and a predominance of type I collagen.



The ALL is present during fetal development, with anatomic and histological features similar to those of the adult ALL.



The findings of this study help to better understand the ALL's anatomy and histology from the fetal period to adulthood. The study presents the existence of the ALL since fetal development, emphasizes the characterization of the ALL, and brings important information to future pediatric ALL lesion studies.
University of São Paulo, São Paulo, Brazil.
Camilo Partezani
CP
Helito
University of São Paulo, São Paulo, Brazil.
Julio Augusto
JA
do Prado Torres
University of São Paulo, São Paulo, Brazil.
Marcelo Batista
MB
Bonadio
Federal University of Sergipe, São Cristóvão, Brazil.
José Aderval
JA
Aragão
Federal University of Sergipe, São Cristóvão, Brazil.
Lucas Nogueira
LN
de Oliveira
University of São Paulo, São Paulo, Brazil.
Renato José Mendonça
RJ
Natalino
University of São Paulo, São Paulo, Brazil.
José Ricardo
JR
Pécora
University of São Paulo, São Paulo, Brazil.
Gilberto Luis
GL
Camanho
University of São Paulo, São Paulo, Brazil.
Marco Kawamura
MK
Demange
D016118:Anterior Cruciate Ligament / Q000033:anatomy & histology*; D002102:Cadaver; D005260:Female; D005333:Fetus; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology*; D008297:Male; D013977:Tibia / Q000033:anatomy & histology*
ACL; anatomy; anterolateral ligament; fetal anatomy; histology; knee ligaments