a poorly tracking/dislocating patella is not the same thing as knee joint dislocation, so we aren't talking about a bone necessary for bearing weight... the patella is present to increase the mechanical strength of the muscles on the front of the knee. if the patella wasn't present, your dog could still walk around, run and play-- but with severly diminished ability of the quadricep muscles... he would have the same amount of muscle, but it would be less effective... so the walk/run/play would be more labored and might encourage movement compensations in other joints.
this patellar issue is very similar to patellar tracking issues in humans. a poorly tracking or dislocating patella is not only a result of the shapes and size of the bony surfaces that the patella is supposed to slide within, but is also related to forces going through the leg and the involvement of muscles of the leg.
you can't change the shape of the bony surfaces, but you can absolutely influence the forces on those bony surfaces.
that means that the condition/situation can be exaggerated, or dimished some degree by several factors relating to force (positioning, movement, muscular pull, activity).
if my dog was going through the same situation, i would want to make sure
#1 every other joint in the leg was working properly, so they could offer ther indirect support),
#2 make sure his weight wasn't too high, as that would increase total forces on the leg,
#3 make sure any activity/exercise he got was micro-progressed
#4 his nutrition was optimal, to ensure the best environment for healing, and
#5 i would investigate chiropractic/accupuncture/homeopathic practitioners that may be able to assess and correct the muscular contribution surrounding the knees thereby restoring some balanced forces and stabilizing or even reversing the patellar alignment