Also here is a quick knee I drew up for you for future reference. Sorry if I’m “flaming” or taking over your thread. Just thought this might help since you said you “can’t” do knees. Hope this helps.
The knee doesn’t need to be defined greatly. Only a little bit. Use soft shadows on them to give them presence but not too much. Sorry for the roughness of my drawing. But I think it gives you the idea I’m trying to say.