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24 m a s s a g e & b o d y wo r k n ove m b e r/d e ce m b e r 2 0 2 3 Here's a fun fact: There's a fifth quad muscle. Who knew? Well, maybe some of you. But I'm only now learning about this, which makes me think two things: (1) What we know about our anatomy is constantly being updated and evolving; and (2) What do we do with this information? I mean, not just that there's a fifth muscle in a group of muscles that were named for the fact that there are four of them, but how does this change our approach? My first thought is more of an ongoing reflection about what we think we know—a great topic of conversation, but not the one I am focusing on for this article. My second thought is more of a question . . . And I have answers. PROCESSING NEW INFORMATION Ultimately, these two points are related. If what we know is always changing, then what we do with that knowledge has to be part of the conversation. In this instance, we have always known the quadriceps muscles to be the vastus lateralis, the vastus intermedius, the vastus medialis, and the rectus femoris. The quads. Four of them. By Allison Denney KEY POINTS • The knowledge that a fifth quad muscle exists gives us a greater ability to be even more nuanced and detailed with our techniques. • Our approach to the quadriceps muscles does not have to change except for this: Learning about anatomy and the muscle's physiologies always guides how we work. THE REBEL MT Five of a Kind Fifth Quad Muscle Can Expand Knowledge and Technique TECHNIQUE Tensor vastus intermedius But now there's a fifth. Where it is and what it does must influence how we work. Technically, there has been knowledge of a fifth quadricep since 2016 (or even before then, but this was when it was officially named). In a study of 26 cadavers, a fifth quadricep muscle, the tensor vastus intermedius (TVI), was found in 22 of them. 1 Technically, not everyone has a TVI. But 22 out of 26 is not a small percentage. Similar to the psoas minor or the palmaris longus, though, anomaly muscles get us thinking: What do they do? What does it mean for soft-tissue manipulation or dysfunction? And, perhaps most importantly, does the existence of a fifth quad muscle therefore change the name of the quads? And so, I give you the tensor vastus intermedius. You will find this muscle (on those who have it) close to the hip and near its similarly named relative, the tensor fasciae latae. Its proximal attachment lies on the proximal and lateral surfaces of the shaft of the femur and/or the greater trochanter—depending on your source 2 — and its distal attachment veers medially and merges with the rest of the quad muscles just above the patella. It's not a vast muscle, though. It looks like the anterior upper-leg version of the plantaris muscle—a burst of muscle fibers at the top with a long, tail-like tendon that reaches down to make contact. 3 The actions of this little muscle are twofold, but not what you might expect. Instead of lending a hand in extending the knee alongside its siblings, it stands in the middle and sort of pulls them back in line if they get too cocky. Specifically, it may

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