"Surgeons discover new ligament in human knee," reads one headline. "The Anterolateral ligament, scientists discover a new body part in the KNEE," reads another. The internet's been awash with headlines like these the last few days. They're all crap. The "previously unknown" ligament in question was discovered in 1879.
According to the new paper describing the ligament — which was led by Orhthopedic Surgeon Johan Bellemans, appears in the Journal of Anatomy and was published online all the way back in AUGUST, for crying out loud — the "pearly, resistant, fibrous band" was discovered and described by French surgeon Paul Segond over 130 years ago (here's the publication, in French). Since then, the band has gone by the name of "(mid-third) lateral capsular ligament," "capsulo-osseous layer of the iliotibial band," and "anterolateral ligament." The authors of this new study find favor with the last of these names, and abbreviate it "ALL."
What this new paper provides is a qualitative and quantitative assessment of the anterolateral ligament's relationship with other, nearby anatomical structures. In other words: How does this ligament, WHICH WE'VE KNOWN ABOUT FOR MORE THAN A CENTURY, function in concert with other components of the knee and leg?
Given its structure and anatomic location, the ALL is hypothesized to control internal tibial rotation and thus to affect the pivot shift phenomenon, although further studies are needed to investigate its biomechanical function.
Biomechanical engineers spend their careers improving our understanding of the structure and function of our various body parts. That's as true for heart valves and knee caps as it is for the anterolateral ligament. Anatomical description ≠ discovery.