Is There a Good Explanation of the Bad Knee?

Evolution cannot be used always to make a good prediction about the features of an organism. Some will be genuine adaptations, but some won't be. It could be that some things are byproducts in for the same reason that hemerglove and has the color that it does. And that could also be why homosexuality continues to arise. I don't know that there's a good explanation of these things too.