Recovering from Getting Hit by a Car

hello all. I am rather a light weight person. 160lbs heaviest at 6ft. I had recently gotten hit by a car and it took time to recover as my injuries were quite severe. now I am new to training. it all started with me starting testosterone (originally sustanon 250 and recently changed to enanthate) at first for depression as my levels were low due to an opioid addiction. now my levels are back to normal and then some as I am now taking 250mg twice a week. I just started larger doses in hopes that depression isn’t the only thing im getting rid of but rather also gaining some muscle weight. now I have a bad knee injury and a shoulder injury that I am dealing with.

I am done with the opioids and small exercises have helped my shoulder quite a bit to the point where the pain is negligiable. however my knee is still pretty bad and I walk with a cain. I am not looking to get huge but just taking advantage of the testosterone I am now taking for depression. I now am taking much more than I need for that in hopes I can gain a bit since I am rather light and slim. what I would like to ask some of you fine people is how I could go about a) strengthening my knee without injuring it further and b) some exercises that would put me on the right path with my right shoulder in the same regard. any ideas? it would be most appreciated if you can help me get off the ground from this point.

I have started mild exercises including freehand weights and whatnot. not more than 20lbs right now as well as squats, situps and small amounts of pushups. I don’t have the luxury of a gym until next month. anyways, what do you think?