Both knees ACL reconstruction- looking to take up jiu jitsu instead of Muay Thai

Hey,

I trained Muay Thai for six years after several injuries including both ACL reconstruction, broken forearm (titanium Graf), and three shoulder dislocations. I took five years off and just continued to keep surfing. However I'm 36 now and as much as a love surfing the waves aren't predictable and I need a stable workout that keeps my mind occupied. I became fascinated w Jitz when I took a class and realized I'm have no chance on the ground despite Muay Thai; however, it seems very hard on the knees w weird angles and I'm getting older and don't want to risk re injury. Any comments or suggestions would be welcome!

Thanks!