The Only right way to do a drawer test to test for CCL rupture is to give them some light anesthesia. Otherwise they can tighten up and disguise the laxity in the ligament. Especially if it is only a partial tear. Don't try to salvage a partial tear with a competitive dog. It will only continue to tear. You will just waste a lot of time and money trying to salvage a partial.
Hope is something easier. And less expensive!