@zoobird1 I just noticed you question and thought I would relate this story: I am in PT for pain management, and am seen in a tiny side practice of a major PT provider in our area. The 3 therapists are specialists in difficult cases, and both leads are doctors of physical therapy. There are no "scripted" routines here, everything is designed for the individual.
This morning in the waiting room, I met a woman with an obviously new knee scar. I asked, she had a total knee replacement of her former (25 year old) original knee replacement - four weeks ago. As a person with RA, and having had the complicated surgery to remove all the old hardware, she was sent to the specialty therapists. Imagine my surprise when I came out of my session to find her in the gym doing step-up exercises on her new knee! Already. I hears the therapist explaining that by doing this with your own body strength, there is little risk of injury. And that it is the best exercise for safely strengthening the quads to support the knee.

So, if it is safe for someone 4 weeks after surgery, I would say it is probably safe for you. Have you asked the PA or PT?
Sue