Hi Bhani,
Good luck - 2 years is a long time to be immobile. I wouldn't expect too much to happen too quickly.
Can your patient do hydrotherapy? The warm water and taking weight off the joint will help.
Otherwise, i would be doing pain-free weightbearing closed chain exercises to develop co-contraction strength and work into their lack of ROM.
I would also be looking at the whole lower limb kinetic chain for problems as being immobile has its drawbacks!
I hope this helps!