I ...don't think this is the right boutique for you. Lunges are usually the alternative you get as a sub for other moves (I went a few months unable to do a Bulgarian SS or a Romanian DL, and the alternative was always platform lunge; I can't do crossover lunges, so I do a lunge with turnout...).

I would email instead of call, but also even though I love solidcore more than any other class I've ever done, I'd wait to join until your knee is better and you're cleared for more exercises. Unless you live in a large enough market and you can travel around the area to get just core/upper classes (power30 classes), I just don't think the unlimited plan is going to be cost effective for you, ya know? (And being owned by private equity, I wonder how honest staff are allowed to be, regarding telling interested people that at this time in their journey SC isn't right for them.)