I worked on getting to straight leg pushups before realizing that the problem was more a lack of core strength than anything else. I really didn't feel my pecs working during straight leg because I couldn't get down low enough to engage them. I've decided that doing them from the knees with good form is all that matters. If I get to the point where bent knee pushups aren't giving me a good burn in the pecs, then I'll need to work getting my legs straight. In the meantime, I need to work on my core!