Sounds like you're doing just that!
But another good one is straight leg raises with the leg rotated outward.
Recline on the floor, supporting yourself on your elbows with your legs extended in front of you. Rotate one leg outward (without abducting) so that the vastus medialis is facing straight up and the heels are still hip width apart, then raise the foot off the floor no more than 12". Hold for 5 seconds, lower and repeat. You can do this with light ankle weights as you get stronger.