Alternative to lunges

I just found out that I have Chrondromalacia Patella or patellofemoral syndrome, in both knees 😑. Sooo I'm supposed to avoid squats and lunges until I build up my VMO muscles, although squats don't bother me as much. So does anyone have any ideas of what I could substitute for lunges when they are in the videos but still be able to get a good workout? I mean summer is coming, and will be here soon since I'm in the south, so my knees trying to sabotage me is really inconvenient since I'm trying to get in better shape for shorts and swim suits lol!