Do your shoulders hurt when doing push- ups? No matter how hard you try, your shoulders always tend to internally rotate, and cause you shoulder impingement as a result.
Ever thought about distributing the load differently on your hands and actually treating them like your feet ?

What do I mean?

Well, if you think about it, distributing the load on your hands more externally, will give an external rotation cue which will eventually help you lock your shoulder blades back together and squeeze your chest out, so that you can perform push-ups correctly. If you actually try it yourself and pay more attention to it, you'll notice that your shoulders will most likely stay externally rotated.
On the other hand (pun intended), treating your hand like a “flat feet” with a collapsed arch and placing the weight internally, will most likely cause your shoulders to rotate inwards through the internal rotation cue implemented at the bottom.