The muscles of the hips cross over bones in all directions, so I think the calves could have the same attachment points and still work from the front.

Muscles of the hip pull in various directions, yes, but that doesn't mean they are located out of line with their attachment points. They are in fact located as directly in line as possible with their attachment points.

All muscles are located this way because any other arrangement would be less efficient. Natural selection optimizes our bodies for efficiency.

The calf muscles pull our heels toward the backs of our legs. The calf muscles are located between those points so they can draw the points toward each other. Any other location for the muscles would be less efficient.

Our lower legs have to be designed efficiently so we can run fast. That's why nature makes lower legs as thin as possible and locates the leg muscles as high as possible. The lighter the foot and lower leg, the faster and longer we can run. That's why animals that run a lot have skinny lower legs and heavier upper legs.

As with all engineering decisions, this design requires a tradeoff. As the lower leg gets lighter, it becomes more fragile and breaks more easily. This is bad. But it's also bad if the animal can't run fast. Natural selection weighed the two criteria and struck a balance.

Now, it's true that some muscles wrap around bones. The supinator of the forearm is an example. When our hand is pronated, the muscle twists around the radius like this:

But still, the supinator is located as directly as possible between its attachment points. The bone is in the way so the muscle wraps around it, but still, the muscle takes the most direct possible path. This is different from what you are suggesting for the calf muscles. Your suggestion would make the muscle lie outside the most direct path.

Edit: I've oversimplified a bit. I should add that some tendons are wrapped with bands of ligaments that redirect the direction in which they pull. The ligaments act almost like pulleys. The muscles that straighten our fingers and lift our toes are in this category. These ligaments allow the muscles to be out of line with their attachment points.

Muscles only pull. They don't push. If your calves were in the front, you would have problems walking. Not sure the foot would even work as it is.

Fellas...shins are the least of our worries. What "designer" thought it was a good idea to hang our most sensitive and evolutionarily critical organs in a thin sack on the outside or our bodies?! I mean c'mon.

I don't think that it is a 'design' flaw, it's just how animals' rear limbs evolved. That's the most efficient configuration.I'm pretty sure that all animals rear limbs are basically the same in structure (exceptions being sea mammals whose hind legs have atrophied).

From birds to horses to alligators to kangaroos to primates the hind leg structure is almost identical - the only difference is length of bone and how we locomote (is that a word?)

The shin question is moot - what we think of as a shin is much higher up on, say, a horse (their stifle is our knee, their hock is our heel) and in much less danger of banging. We aren't THAT far from our 4 legged stance (in evolutionary terms).

So a horse is short from hip to stifle (knee)long from stifle to hock (our heel) and from hock to fetlock (our toe joint) and walks on his single toenail. A kangaroo stands upright like us but is also long from stifle to hock and hock to toe joint and hops.

Primates are long from hip to knee and knee to heel ... but then we have very (relatively) short bones from there and we walk in our unique heel-toe gait.

Same bones structure just different parts on the ground and different movement.

It was set the same way hundreds of millions of years ago and all of us - alligators, kangaroos, horses, and humans have evolved differently to use it as best suits us.

Sorry so long! This stuff fascinates me. :D

There's always one satyr at every party.

Because if you bang your shin, it will have little to no effect on your reproductive ability. You'll survive the bang and still pass on the calf/shin genetics to your offspring. We can only evolve with the genes we have, which call for a calf in the back (as another reply stated). Natural selection for traits tend to select for genes that are potentially in the genetic code (barring a beneficial mutation of some sort). Then you must add in the the ability to pass on that code to offspring. Basically, we work with the genes we are handed down, and if we can tweak them for a reproductive advantage, then changes may occur but otherwise, we'll just go on banging those shins.

To push forward they would need to be in the back I believe. I'm no anatomy expert, but I don't know how they'd push us forward from the front.