Knee replacement is pretty common these days.
1) your knees will keep getting worse, as you walk to classes
2) options: full or partial knee replacement
Depending on the state you live. If you were any where near Memphis, TN I’d recommend Dr. Lawerence Schrader. He’s done both my husband’s Partial knees. And one was on the back side of his 1-4 scale. Just did my Son in laws, and he’s a 6’6” man, 200 lbs, with calves the size of my thighs, from having had diabetes, heart issues for years before stomach reduction surgery to loose 200 lbs. He is back to work, had a wet floor fall, but no damage to the leg repair, in under 2 months. PT is done at home and walking. Only 1 who does this type of surgery. Even his full knee is superior to those offered by most orthos.
You can walk the same day, drive in 3. Climb stairs in a week, Kneel back most of the way. Lots more rotation than regular full knee replacement and just as strong.