Researchers Discover New Knee Ligament

A team of researchers at University Hospitals Leuven in Belgium have named a previously undescribed ligament in the human knee. One could even say they discovered a new body part.

Despite successful ACL (anterior cruciate ligament) repair surgery and rehabilitation, some patients with ACL-repaired knees continue to experience pivotal shift, or episodes where the knee gives way during activity. For the last four years, orthopedic surgeons Steven Claes, M.D., and Johan Bellemans, M.D., Ph.D., have been conducting research into serious ACL injuries in an effort to find out why. They found that this previously ignored ligament could be the cause of this pivotal shift. Their research was published in the October issue of Journal of Anatomy.

According to the abstract, in 1879, the French surgeon Segond described the existence of a “pearly, resistant, fibrous band” at the anterolateral aspect of the human knee, attached to the eponymous Segond fracture. Till now, this ligament was largely ignored, called such confusing names as “(mid-third) lateral capsular ligament,” “capsulo-osseous layer of the iliotibial band” or “anterolateral ligament,” and no clear anatomical description has yet been provided. The research team studied 41 cadaver knees and found the ligament to be present in all but one of them. The researchers settled on the name anterolateral ligament (ALL).

“The anatomy we describe is the first precise characterization with pictures and so on, and differs in crucial points from the rather vague descriptions from the past,” Claes told LiveScience. “The uniqueness about our work is not only the fact that we identified this enigmatic structure for once and for all, but we are also the first to identify its function.”

One type of pivot shift occurs hand in hand with a lesion to the ALL, Claes said.

“If the lesion would be overlooked or untreated, this might be the cause of persistent instability after traditional ACL surgery in highly instable cases,” he added.

Claes said that he does not know for sure why the ligament has been ignored for so long. Perhaps it was due to poor dissection techniques; or degradation of the ligament in older cadavers; either way, its discovery paves the way for progress in understanding knee injuries better and improving knee surgery techniques.