I really don’t mean to sound like a creepy perv… but on a number of observations on several occasions, I’ve always noticed this one bulge a little above the knee. It’s more visible from behind and it’s located on the inner part of the thigh. (I think I might have drawn it a little too high) It’s even visible when you’re looking at the leg from an outward angle from behind.
I’m still not sure if it’s just a muscle or has some bone and fat involved. One thing’s for sure, it’s a very prominent feature of the leg.
Loomis seems to identify it as the sartorius, but from what I recall from comparative anatomy, and what I read from Wikipedia, the sartorius is a very thin strap of muscle. It couldn’t possibly cause a bulge like that. If anything, the sartorius probably wraps around whatever it really is.
I have a hunch that it’s mostly just the vastus medialis… but it might not be as simple as that. Or it might not be it at all. Anyway, the point is that it’s there. I’ll update this post when I find out what this is.
Double Edit (2/27/2010), (6/15/2010):
After over a year and some thorough studying of human anatomy, I think I’m a bit more qualified to identify what causes this bulge.
Of course, from the perspective of a person concerned with only a little more than how this “inner thigh bulge” looks, it might be enough to measure it across different people and get its typical size, shape, proportion and location.
For other people still, it might suffice to know that it’s there so you can begin to pay attention to it. Knowing that it’s there at all can go a long way in helping you study it yourself.
As for the people who are interested, allow me to explain in the most concise way possible:
Legs, much like arms, are comprised of many structures: bone, muscle, fat, connective tissue and the necessary vessels and nerves to sustain their structure and activity.
The inner part of the knee joint is where the thigh bone (the femur) and the larger lower leg bone (the tibia) meet. The femur and tibia are kept apart from each other by pads of fat and fluid but are attached to each other by ligaments and by the muscles that extend along the length of the thigh and the lower leg. The bones, the pads, the muscles and how they’re arranged in relation to each other all contribute to its shape:
- The Quadriceps (picture) is a set of four muscles named according to their size and location: Vastus Lateralis, Vastus Intermedius, Vastus Medialis and the Rectus Femoris. They wrap around the front of the thigh and are attached to a shared tendon that wraps around the kneecap (patella) which then attaches to the front of the tibia. The Vastus Medialis, which can be found in the inner part, contributes to the bulk of the inner side of the knee.
- Notice the two bulging ends at the bottom of the femur. These are called called epicondyles. (“epi” meaning “over”, and condyles referring to where two bones slide against/hinge with each other). Take a look at how the medial (inner) epicondyle is considerably larger than the lateral (outer) epicondyle. This relative size of the medial epicondyle of the femur also contributes to the bulk of the inner side of the knee.
- The hamstring muscles are muscles at the back of the thigh (opposite to the Quadriceps in location and action). They’re made up of the Biceps Femoris on the outer side, and the semitendinosus and the semimembranosus on the inner side. The semitendinosus and semimembranosus on the inner side contribute to the buldge.
- The thighs and knees (especially the inner side) are also places where fat deposits are abundant, especially in women, contributing to the bulge.
* – note that I’ve used the terms “inner” and “outer” to refer to the more anatomically accepted terms “medial” and “lateral”. Please refer to the anatomical terms of location page as I will use standard terms from now on in an effort to achieve clarity (and expand my readers’ vocabulary).
