Untreated sports injuries & exercise

Until I realized that I would have to spend the rest of my life in this body, I treated my joints pretty roughly; I have damaged EVERY joint in my body in one way or another and most of the injuries have never been treated.  For instance, right now, I am dealing with a torn rotator cup in my right shoulder, torn cartilage in both knees, torn ligament in my left knee and ankle, and various injuries to my hands and wrists.   My big concern, however, is how I can work around the instability in my left knee that was left behind after I tore the ACL.  I have been involved with martial arts for about 20 yrs, but for the last 15, I haven't been able to use my left leg; I'd like to be able to strengthen it up to the point that I can be confident in using it again.  Anybody have any suggestions?

My karate master had lots of surgeries on his joints. I just dropped out when I kept crying during training just from my own joint issues. 2 years later after much rest and Glucosamine until I could move again. I'm slowly rebuilding. I would like to get back to karate, but I really have to get my body in shape first. I'm making progress but I know I could not stay in low stance and execute the kicks I used to at this point.  In all I do, which would include if I get back into karate, I have to be careful not to overstress those joints. The wear and tear over the years will not keep me going if I don't.

That is exactly my point....you know exactly what I'm talking about.  I have a very hard time even jogging because it is so unstable....I'm hoping that it will stabilize somewhat after I have taken off a few pounds.  Cross your fingers!

I found it very difficult to give my body time to heal. My training experience caused my mind to push, push, push.  Which is partially why I quit training all together.  You are probably very in tune with your body, but if you are like I was, I tended to ignore or override some of what it was telling me.  Now what I do is identify what it is telling me, workout if it feels right and see if it improves or not. If not, I totally back off.  For me the worse issue was my knees which have been a problem since high school. So after my resting phase, I came back with Curves (women only--sorry) which I was able to do with minimal pain. I tried swimming but that was hard on my shoulder. After a couple of weeks of Curves I saw improvement in my endurance, which was disgusting! I'm able to do a lot more but during biking and weight training I pay particular attention to the joints and keep the weights light. My endurance is increasing and I'm no longer embarrassed about it. But it is still going to be a while before I can out last all but the well trained karateka. 

Instead of jogging try walking with bent knees--sort of like doing front stance it gives you more resistance and large muscle workout plus helps build up the muscles around those joints.  I also would stand in lines using a very short back stance. Every calorie burned.....

I have a tendency to "over-exercise", but something that helps with your joints is changing up your cardio so that you are doing training with impact index. For example, I play soccer 3 days a week, so I don't bother with running/jogging because it really starts to cause pain in my joints. So instead I will rollerblade, swim, bike etc.

Both are very good advice...Thank you both!  I'll have to try these!