with your age, talk to your doctor and to a personal trainer. They will be able to find the best solution for you. It is much more complicated when you are growing, because like you mentioned, it can be damaging when you are growing. My freshmen year of college, I began lifting a lot more (used to play sports and do workouts for that/practice), and I found that doing legs 3 days a week for the whole semester made a noticeable difference in my skiing. No pain anymore (knees used to crack and I would sometimes walk weird on mondays after long weekends skiing), and I just felt like I was much better overall at skiing. I could jump higher, I could go faster, I could do moguls for much further without stopping because my legs were tired etc. So if anyone else my age is reading this, I suggest that. To OP though, talk to the doctor and a trainer.