Heck, maybe moving up a weight class by adding a little muscle on to become more powerfule and stabilize joints that have been injured wouldn't be such a bad thing. Ususally, the higher the weight class, the less zipping around the ring you have to put up with. With you getting over a knee injury, maybe boogeying around the ring even just a little less might help your knee out.

Sorry for all the maybe's. I haven't got to actually see much in the way of female bantam and junior bantam weight fights to be able to determine how much difference there is in ring movement.