Yes it is possible; it is relatively easy to find video of people doing it. I am not a health professional and I would not presume to give health advice, but I am an aging practitioner with knee issues and I share your concern over the posture. Squatting on that right knee can be challenging.
As I said, nothing below is medical advice; I'm merely relating some things that I do to protect my knees. Your challenges may be different, and you should consult your instructor/medical professional/tax attorney/life coach as appropriate.
I ensure that my right knee stays over my right foot as I squat. Sometimes I need to turn the right foot inward a bit before I squat; I believe this compromises the purity of the posture, but protects my knees.
I also don't squat as low as I would like to; I listen to my knee and limit my practice to what my knee informs me is realistic.
I probably won't articulate this very clearly, but in my experience it is vital to warm up the qua. The degree to which I can "open" the posture without compromising the structure of the knee joint depends heavily on the flexibility of my qua. If I want to open my posture to 90 degrees or more, I find that working to warm up and stretch my qua is more effective than working my knees. (I suspect that my knee are nearing their end-of-life; there is very little left I can do other than to avoid damaging them further)
Does that help?
To respond to Mattm.... I'm making some assumptions. for squatting single whip/snake creeps down, I actually start with my right foot just beyond the cardinal and my left leg at slightly greater than 90. In order to practice isolation, I put all my weight in my right leg and slide my left heel out as I squat. At my age if I can get three to five inches of squat I'm content. I'd love to open up the posture, further as I squat, but realistically, I'm not going to be able to create a greater than 90 degree angle between my right foot and left thigh.
(of course it is easy to get into squatting single whip; the trick is to get out of it in a controlled and safe fashion. There are plenty of postures that I can do once if I'm willing to pay an orthopedic surgeon afterwards).
Hope that helps - it is possible that I've completely misunderstood the question.