Hi, perhaps your Vet could maybe feel some "looseness" around the joint, this could be a pre curser for future knee problems or on the other hand may not get any worse. If I were you I would err on the side of caution and maybe start to do everything you can to strengthen the joints and ligaments around the knee which will only be beneficial for Domo anyway. You can do this by ensuring he gets regular exercise, particularly walking on inclines, swimming if it is possible and a good quality joint supplement are all good habits to promote joint strength. I wouldn't encourage a lot of jumping but the use of steps etc is great.
Willow, Bella & Alfie