You might also be thinking that this title is merely “click bait”, but actually it’s not. It’s legit. There are truthfully five (5) muscles that comprise the quadriceps femoris group. What’s even funnier than the fact that the name is no longer accurate, is that this “new” quadriceps muscle has been described in studies of human anatomy at least since 1987. (referenced in this study on page 238).
Even in the previously referenced paper, which was authored in 1990, a new name has been thrown around. “Quintceps”. Yep, doesn’t it sound cute!? After saying quintceps, “quadriceps” just sounds so dull and harsh…
Anyway, moving on.This extra muscle is snuggled in between the vastus lateralis and vastus intermedius muscles. It’s called the “tensor vastus intermedius” or TVI for short. It is fascially distinct from the other muscle bellies of the quads/quints, and it also has it’s own distinct blood supply and innervation from the other components of the group. A recent, and clearly more popular study than the original ones, examined 26 cadavers and found this to be consistent in each and every one. (That study can be found here).
Whether this muscle is a newly evolving muscle, or whether it’s been there forever is a topic that I’ll leave you to speculate on. It appears that in the earlier examinations (1987), there were variances and not all cadavers had the 5th muscle belly, where in the more recent examination this muscle was found in all studied bodies.
So what does this mean, and why is it important?
It means that you should be able to lift more weight with your legs. You’ve got more muscles now!
No. I’m kidding.
The implications of this knowledge are yet to really be determined. Clinically, we have yet to fully understand the role of this particular muscle in the spectrum of therapeutic treatments. It could be nothing, or it could open new methods of manipulating the tissues for greater therapeutic benefit.
However, this finding or rediscovery does highlight to us that we are constantly expanding and changing our knowledge of the human body. As a result, it reminds us to be a little more malleable in our mindset when it comes to anatomy, physiology and the sciences of human biology.
Besides that, the name “quintceps” surely enriches our lives.