It was surprising when scientists discovered a new part of the human body earlier this year, but understandable that it had gone undetected for so long given that it’s only 15 microns thick (it’s in the eye). But another, larger part of the human body will now need to be added to anatomy books.

A ligament has been hiding in the knees of most — but not all — people.

A French surgeon in 1879 speculated that an additional ligament might be located in the front of the knee, but it wasn’t until 134 years later that Belgian knee surgeons have identified it.

The newly identified knee ligament, which was thought to exist for more than a century but just recently proven, is called anterolateral ligament. (Image source:

The newly identified knee ligament, which was thought to exist for more than a century but just recently proven, is called anterolateral ligament. (Image source: University Hospitals Leuven)

For four years, Dr. Steven Claes and Dr. Johan Bellemans, orthopedic surgeons with the University Hospitals Leuven, researched ACL tear repairs and “pivot shift” issues — when the knee gives out — that seemed to be related.

Claes and Belleman’s found the new anterolateral ligament (ALL) in 97 percent (40 of the 41) of cadaver knees they studied. Further research showed this “pivot shift” was the result of an ALL injury.

The discovery of ALL clarifies what the study authors called in their abstract a “long-standing enigma” regarding a ligament connecting the femur with the anterolateral tibia.

The new find was published in the Journal of Anatomy.

Going forward, Claes and Bellemans are trying to develop a surgical technique to correct ALL injuries.

Featured image via Shutterstock.

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