Clearly you can do it, because you've done it. Easing into it makes sense, though. I suspect your knees will get used to it. I do dead lifts almost every day, and that helps me. I'm 57 years old and now need to do weights to maintain my strength.

But you should solve the numb hands problem. Don't let that go on. Go to a bike shop and ask them to look at you on your bike. See if they have suggestions.