As impossible as it may seem, two surgeons at University Hospitals Leuven have discovered an entirely new part of the human body. It is a ligament in the knee and it appears to play a role in patients suffering from a tear in their anterior cruciate ligament (ACL), a common sports injury.

Named the anterolateral ligment, it was discovered using macroscopic dissection techniques after the doctors began investigating possible causes for complications after rehabilitation for ACL. They came across a paper written in 1879 that hypothesized the existence of a previously unknown ligament in the knee. The author of the paper turned out to be correct; Dr Claes and Dr Bellemans managed to locate the ligament and claim it can be found in 97% of all patients. Further research found that the pivot shift, a common complication after ACL rehabilitation, is caused by a tear in the ALL ligament.

The last time a new human body part was discovered was June 2013. Although just microscopic layer in the human cornea, its discovery made eye surgery simpler and safer.

We have a tendency to believe we know everything there is to know about the anatomy of our bodies - after all, we've been studying them in great detail for hundreds of years. These discoveries prove there's always more to learn, and every new piece of information helps patients and doctors.