Bench Step overs
Single Leg Split Squats with dumbells or bodyweight
Lying leg raises with the toes pointing slightly laterally
You can also put a small ball in between your knees when doing bridges, the squeeze will help work the Vastus Medialis more.
If there is any sort of knee degeneration it is more difficult to train the Vastus Medialis.
Here is a good link to check out for more information. Hope it helps 🙂