For now how about riding a bike at an easy pace ... if you can't complete a full revolution, do half ones ... forward until range limits, then backward until range limits.
Also, quad sets and straight leg raises would be good and you can continue to do RDLs but I wouldn't go too heavy.
Make sure the knee is good and warm before working it ... the bike would be good for this, or you could use a hot pack, and ICE afterward.
Keep us posted on what the imaging results are ...
