I would ask your physiotherapist if it's likely that you're going to have alignment isssues because of the structural damage to your bones. I would get them to give you an exercise regimen, that's their responsibility, given the infrequency of your supervised visits at therapy, the "plan" should be a home-based therapy program with "check-ins" to evaluate progress and develop new exercises etc. You should have exercises for quads, hamstrings, calf, ankle, hip, etc to be done twice a day. You're gonna have to step up and make them set it up for you, if they've not done so. Don't leave the next appointment without exercise sheets! Tens unit could be helpful for targeted muscle atrophy, if you're having trouble reengaging the quads, etc, but only the therapist can ascertain that.

As for a brace, if the knee is that far twisted if you're putting full weight in it, you may need a structural brace with hinges on both sides. You could try a sports brace with the metal hinges in it, as an experiment, since they're not very expensive, and if it helps, look into seeing if a custom brace will be needed long term. Again. your OS and therapist  are the best sources of input on the topic and if it would be a good temporary or permanent aid.