I recently had the same thing happen to me as Barbara from Portland, Oregon below.
Ten years ago I tore the meniscus in my right knee. If I was careful, I could manage the pain, but could no longer do the hiit exercises that I enjoyed. No jumping or squatting, or I would be up all night from the pain. I tried all the supplements that Barbara wrote about, plus all the types of collagen. Every time that I thought I sensed improvement, I would get more adventurous with my exercising only to find out quickly that I had been wrong.
Two months ago, I started taking 6 grams of vitamin-c to see if it would help me to avoid covid. One day, I realized that my knee felt better, so once again I tried adding the exercises that had caused painful flareups over the last ten years. Nothing happened. I gradually became more aggressive, but the knee held up. I am now back to doing routines that I had to stay away from for so long, including some of Cathe Friedrich's advanced step workouts, which had been totally off-limits. There are times that I feel a little bit of soreness, but it is always short-lived.
I don't know why it has worked, but I am grateful.
I started taking high doses of Vitamin C to help ward off a cold virus. For the past several weeks I took 5-10 grams of Vitamin C. Then I noticed my knee pain disappeared.
I am a runner/cross country skier who has virtually stopped these activities due to pain in my right knee.
For 7 years I have tried glucosamine, calcium, MSM, and NSAIDs. I don't like taking NSAIDS. However, the other remedies did not relieve the pain and inflammation. Therefore, I have been tolerating the pain and have discontinued using NSAIDS.
I was very surprised to find that the Vitamin C use correlated with complete pain relief and reduction of inflammation. So I stopped the C for a week and the pain returned. I have resumed the C and the pain is gone again.