open talus fx

in april I underwent surgery to repair the tendens and talus. after being in a cast for 10 weeks its stiff and sore. I have now had almost 8 weeks of p/t at 4 times a week but am still very stiff. I reciently began showing signs of osteoporosis and early sclerosis in the talus dome. does this affect how I should work the ankle? or is there anything else I can do to help restore movement? right now all they do is whirpool, stair stepper and tredmill.