Osteoarthritis In The Knees

Hello, I have always been athletic with baseball, wrestling, a little cross country running in my younger days and mostly bodyweight exercises in my adult life and felt great until one day I had terrible pain in both knees when I went for a walk. I subsequently got diagnosed with stage 4 osteoarthritis by two orthopedic surgeons. I went to a posture specialist who corrected my walking form and now I can walk without pain, but perhaps due to bad walking form over the years and a cheat diet that includes Snickers bars and other fun food the damage is done. While the posture expert fixed my biomechanics so I can do things like go for walks without pain, sometimes I feel the arthritis in my knees for example when going up and down stairs or when carrying heavy objects if my knees are not warmed up. Luckily my knees don't bother me when just sitting or lying down. I'm not on any medication or pain killers because I don't need them. I guess I'm lucky in that regard even though I have stage 4 osteoarthritis in both knees. What supplements can I take to stop progression of the arthritis and even reverse it? Also, are there any exercises or food you recommend to help the process? Thank you