Having a bent elbow as you prepare your backhand stroke does not indicate that you're leading with your elbow. You need only watch most of the pros with great one-handed backhands to be reassured. If your bent elbow juts forward, then you swing your lower arm forward by straightening at the elbow, that's leading with your elbow. You can simulate this motion by pretending you're hammering a nail into a wall at waist height. What you're hammering when you do this on a tennis court are the tendons around your elbow.

