I’m sorry to hear about your knee trouble, man. I think most people on this site can attest to what you’re going through (myself included) and we all wish you the best in getting back to full strength.
Concerning work for the Vastus Medialis, there are three modalities that are normally used in succession to “bring up” a lagging VMO: soft tissue work, motor control, and strength training.
When a knee undergoes any sort of acute trauma - like a torn tendon - the VMO has a tendency to just shut off and fire erratically, which leads to faulty motor patterns in the surrounding musculature. For this reason, your first two courses of action should be to lengthen the tissue (via foam roller, stretching, massage) and then reclaim the motor control with an exercise called the close-chained terminal knee extension (TKE).
Check this video out, which does a pretty good job of explaining the TKE ==> http://www.youtube.com/watch?v=ZscBVtoX62U
So maybe say a good 1-2 minutes of soft tissue work on that quad followed by 3 sets of 12-15 of the TKEs is how you should start your lower body sessions for the next little bit. After that, feel free to transition into strength training that you feel comfortable with. If you’re not sure what your knee can tolerate, follow this single-leg progression and stop at the appropriate level:
- Isometric Hold
- Split Squat
- Reverse Lunge
- Dynamic Lunge
- Bulgarian Split Squat
- Single-Leg Squat
Hope that helps, man. If you have anymore issues, I highly recommend you pick up Mike Robertson’s “Bulletproff Knee” manual, which is about as comprehensive a resource of post-PT knee rehabilitation that I’ve come across.