Getty Images / Silvia Otte The new body part, named the anterolateral ligament (ALL), may lead to new treatments for ACL injuries.

In an age filled with advanced medical techniques like MRIs, artificial hearts, and laser eye surgery, one could be forgiven for believing doctors are also at least vaguely familiar with every one of your body parts. However, a new discovery by Belgian physicians has proved this assumption wrong.

As Science Daily reports, two surgeons at University Hospitals Leuven have located a new ligament in the human knee, and their findings may mean a revolution in how we treat ACL injuries. Dr. Steven Claes and Professor Dr. Johan Bellemans have spent four years trying to solve a modern medical mystery: in certain cases, patients who have had their ACL repaired still experience “pivot shifts” in their knee, where the joint “gives way” during physical activity.

In order to find their answer, the scientists turned to the past. In an 1879 article, a French surgeon theorized that there may exist an extra ligament in the anterior of the human knee. Using macroscopic dissection techniques on a wide range of cadavers, the Belgian duo confirmed this hypothesis. According to their findings, 97 percent of humans have something called an anterolateral ligament (ALL) in addition to their ACL, and pivot shifts stem from an injury to this previously unknown body part.

This discovery could mean a breakthrough in treating ACL injuries, which are common in sports like basketball, football, and soccer, where pivoting is common — but don’t hold your breath for a better fix. Claes and Bellemans are hard at work figuring out surgical to techniques to repair the ALL, but Science Daily cautions that those results will only be ready in “several years.”