Tai Chi is easy to have bad knees, because it emphasizes the routine norms too much, and the novice strength is not easy to go wrong.

I suggest you find out the master's riding steps first. Maybe you'll say riding on your knees is unbearable. In fact, there are high and low horses. Knowing that the master is willing to take you will help you step by step. But you have to figure it out for yourself, because people with weak constitution need to exercise first to keep fit, which requires much more effort, hard work and brain power than others!