you're very young to have dodgy knees,? will they get better??
I was 16 when I ripped ligaments in my left knee and 18 when it was operated on which resulted in losing full use of the knee. I then spent almost 15 years using stairs one at a time, unable to kneel, squat, run etc.
Losing weight reduced the overall strain but it's been biking that has built up the muscles surrounding the knee and strengthened the leg generally (which is still much thinner than the right due to years of under use and muscle wastage). I still can't kneel, squat properly or run but can use stairs normally.
The right knee used to suffer the same dislocations but I never ripped the ligaments like I did in the left and after the poor result from surgery on the left knee, I refused it on the right. I now suffer from osteoarthritis which results in crepitus and pain in both knees, esp in the cold or cramped conditions. Riding (esp pillion) for long distances can be very painful due to my knee armour putting pressure on my left knee in particular.
It’s a lot better than it used to be but I think this is probably as good as it’s going to get and I can look forward to further problems in future as I get older.
For now though, I'm just grateful that they've improved enough for me to ride a bike and in turn, riding that bike has improved my knees and overall strength and fitness.