Ah looks like you picked up an error from my edit.
Scrappy line edit (ignore lighting):

Still wouldn't recommend that as a reference but hopefully it helps correct a few things in the quad muscles and knee.
Here's some references that will hopefully help:
http://www.muscleandfitness.com/sites/muscleandfitness.com/files/styles/large/public/Quads_2.jpghttp://vallejo.ural.net/1997/002a.jpghttp://aldgerrelpa.deviantart.com/art/Wun-Dar-342309711http://bida999.deviantart.com/art/Night-Monster-final-196986238Lets refer to Sagat below done in cartoony style pixel art for some other tips:

- You don't need to draw a line between every muscle. Remember there's also a layer of skin smoothing things out no matter how buff the guy is (hmm skinless body builder could be fun:

. Sometimes you can just imply lines by how the light and dark works. Notice there is clear areas of light and dark? There's lines where the angle is greater and the rest is implied. Shadowy areas tend to have less lines since there is less light there.
- Dark lines are generally not used in the lighter areas, just the next darkest shade.
- Don't highlight every single muscle. It makes it kinda look like a bunch of bumps popping up from an otherwise flat surface. Notice Sagat doesn't even have the lightest shade anywhere below his shoulders? They've picked a useful light source to work with here and followed through with it. Notice in Ax-Man (
http://aldgerrelpa.deviantart.com/art/Wun-Dar-342309711), a different but still very clear light source with only selective highlighting.