I think I should point out that it's normal for there to be no muscle in front of certain parts of the shinbone! If you follow the sharp edge which runs along the middle of the front of the lower leg, you shin bone (tibia) IS covered by muscle on the outside of this line (it's mainly the tibialis anterior muscle, but it really is just bone and connective tissue to the inside of that midline, until you get to the gastrocnemius and soleus, bulging from the back. Not easy to put into words, but I'm just wanting to say that you can't build muscle where there isn't any!
I'll try and find a picture.