In a study published in The Journal of Clinical Anatomy in January of this year, researchers have discovered an independent quadriceps muscle, the tensor vastus intermedius, or TVI. The researchers noted that past clinical texts of the quadriceps muscles were not in line with what they had seen in cadaver research, thus spurring the study. The quadriceps, or quads, are comprised of four muscles. The rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis. They are located on top of the femur starting around the hip and inserting just below the knee on the tibia, encapsulating the patella (also known as the knee cap).
Function of the Quads
This group of muscles is among the most powerful. They help to extend the knee and flex the hip. These roles are crucial to helping in the most basic of movements from walking and running to the explosive actions such as plyometric movements, and squats. They also assist in stabilizing the patella and the knee joint on the whole and function as an antagonist to the hamstring group located on the posterior aspect of the leg.
The Tensor Vastus Intermedius (TVI)
According to the study, 26 cadavers were researched, and each one was discovered to have the TVI. It sits between the vastus lateralis and the vastus intermedius. It has also been discovered to have its own vascular supply, cementing the TVI as its own muscle. Researchers in the past had known about this tensor, yet had not recognized it as an independent structure until now. This begs the question, why has no one figured this out before? According to Dr. Jim Gilliard of the Ontario Chiropractic Association in Canada, it’s located in a section of leg that is not really known for surgical intervention. Thus, it is unlikely that there has been detailed exploration. Also, if you look at the structure close up, the muscle bellies are very, very close together, and the structure can vary in part in different people and even within the same body.
So, What Now?
Well, really nothing. More research will undoubtedly come to light in the coming years on the TVI and its function in the muscle group. However, it’s just really mind blowing to think, considering how long cadaver research has been going on, that in 2016, it can be confirmed that a new independent muscle has been there the whole time. Granted, this is not the first in our time that a new muscle has been discovered. In 1996, a new muscle was reportedly found deep in the skull, and in 2013, a previously unknown ligament in the knee was discovered. It is all very fascinating, to say the least.
A Personal Side Note Regarding Cadaver Research
The human body is constantly terrifying and amazing me to no end. When I started my cadaver anatomy class a few years back, I was filled with thoughts of The Walking Dead (the series had just premiered on AMC, and I still can’t watch it). When the class was over, I was profoundly changed. People had given their most precious commodity, their bodies, up to science, so students like myself, my sister (a science teacher), and countless doctors, biologists, anatomists and many others to know humans better.
For that most selfless gift, I am forever grateful, and I plan on returning the favor one day.