This week: Leg Muscles
If for this week's post about the legs I had done nothing but write "The femurs tilt in.", I'd have still improved the figure drawing of many people reading this immeasurably. Drawing the legs as two straight lines coming down from the torso has led to more frustration than just about anything except maybe feet and hands for just about every cartoonist. Drawing the legs straight when you stick-figure in your figure works for standing poses okay, assuming your figure is really cartoony or is wearing pants. But when you try to make that figure run, or get into an odd pose, things get pretty hairy and you start doing that re-draw-it-20-times-and-it-still-looks-funny thing. God help you if you tried drawing realistic muscles on a figure using straight legs as the basic shapes. It looks lumpy and wrong and you sink into confusion, frustration, drinking and suicide.
This week, I'll show you what's going on inside the legs, and what gives them that weird effect where they seem to form a straight line and yet aren't straight at all.
Let's start with the bones. Here's the pelvis we learned how to draw, remember? Now, pick where your knees are gonna go for your character. in a stock-straight standing position they'll be under those loops of bone at the bottom of the pelvis called the ischiums. The knees are pretty thick, so draw something thick where the end of the knee bone's gonna be. In this position the feet will come below those, so mark them off. These 3 points, the ischiums, the knees, and the feet, form the "straight" line of the leg, and are what make all the crazy curves the leg takes seem straight while being very obviously curved. The leg does NOT form a straight line from the hip joints, like you might think.
Now, to get the angle of the femur, draw your dots representing the greater trochanters, which is where your femur stops going slant-ways out from the joint and heads down. (draw them somewhere wider than the pelvis is wide and somewhere in the neighborhood of the ischiums in height.) Then draw a line from there to the INSIDE of the knee. Now you have your slant.
Now draw slightly bowed-out lines from the inside of the knee down to the foot dots. These are actually too curved, I'm exaggerating a bit for effect. (although I like to curve them when drawing a figure because it makes the shape of the lower leg easier to draw)
Now that's all you really need if you're just using these as guidelines for your figure drawing, but if you want to make bones, add the crested caps to the bend in the femurs (important for muscle attachment) and fill in the tibia at he knee joint. It should be about as wide as the corresponding part of the femur above.
Now fill in the fibulas under the overhang of the tibias, and fill out the femurs, and change your dots into heel bones. Now you have bones!
Now, the curves the bones take can seem pretty crazy, and it's hard to see how they come out to looking like a straight leg. When you draw a leg wrong with straight bones and then try to add muscles the muscles bulge out horribly. But when you draw muscles into the spaces of the crooked looking leg bones of a real skeleton they even everything out and make it appear straight and natural.
First, we start with the bones: (click on these to see them larger)
Deep in your legs, coming from the ischiums, is a sort of fan of muscles that attaches up the entire inside length of the femur. (There are a LOT more than this, but unless you're drawing very realistic groins you only need to know these as a packet of muscles to get the shape of the leg right.) It's amazing how much more leg-like the skeleton gets just adding these isn't it?
The next layer of muscles:
Front- Vastus lateralis on the outside and vastus medialis on the inside are the two quad muscles that make muscle men's legs seem creepy and lumpy above the knee. Nomuscles pass through the knee, only tendons of muscles, and so muscle bulges around the joint while the joint stays looking pretty much the same. They attach on the greater trochanter.
Back- Semi Tendinosus on the inside and Biceps femoris on the outside form the two muscles whose tendons shape the back of your knee and the back of the thigh. See how just with them there it looks like an almost complete knee joint? There you go. They originate from the ischiums, pass as tendon over the the back sides of the knee and then insert below the joint. These muscles act like the bicep muscle in your arm, bending the knee. It even has two parts just like the biceps. Hmm.
Front- Completing the quad muscles and the front of the thigh muscles are rectus femoris and satorius. They both come from the crest of the pelvis. Rectus femoris keeps the other two quad muscles visually separate and turns into the huge tendon that houses your patella (knee cap) and goes down over the front of the knee joint, basically defining the shape of the entire front of the knee joint. Satorius curves around the quad packet and curves along the inside of the knee, adding a little curve where you'd otherwise see bone. For clarity I colored it red as it passes down the side of the knee, but in fact it turns to tendon as it passes over the knee like everything else. The quads act a lot like the triceps muscle in your arm, straightening the leg out or pulling it up from the hip. Also, it has a huge tendon like the triceps and has 3 parts like the triceps. Hmm.
Back: Gluteus maximus, your famous butt muscle. It originates on the pelvis along the iliac crest of the spine, all the way back and down the tailbone, and inserts along the back of the femur. How far? Well, I made this drawing extra see through so you could see the bones underneath. The gluteus maximus should totally cover the ischiums as it slants down to meet the femur.
Now the lower legs:
Front- over your fibula and on the side you have a bunch of tendons that operate the foot,, toes and ankles. No need to go into them, just think of them as a packet of muscle giving shape to that part of the leg.
Back- The calf muscle is two lobes that come from both sides of the knee joint, adding shape to the back of the knee, then down where they swell out, the inside lobe being thicker and lower, and then tapering into a single, powerful tendon called Achilles tendon that attaches to your heel bone to draw the foot back, like if you were to stand on tip-toe.
Here's what the front and back muscles look like with all the muscles filled in:
Looks like a leg now, right? One more thing to note while drawing the leg using bones, the leg has a lot more mass in back of the femur than in front of it. Much like with the arm, the quads/triceps aren't quite as massy and thick as the biceps/back of the legs.
Well there you have it, the leg!
Next week: The final part of these anatomy lessons, where I address the neck and other odds and ends I haven't touched on yet.