I've been protecting my knees for years. I don't do a lot of running or jumping and I am wary of deep squats or explosive jumps. Skipping is ok as you are absorbing all the shock with the foot and calf, same for the elliptical cross trainer.I probably should see doctor about my joint problems and fear it may get worse.
I'm scared to do any cardio exercises like running,jogging,treadmill, elliptical, jumping rope,going up hill so on because of the impact on the knees.
There is also the probability because of the sedentary lifestyle I may have done damage to my joints or I lack muscles for those work outs. And need to hit the gym and start lifting weights before I can do any thing.
Hit the gym by all means but I would be staying clear of most of the weights.