What can you do to reduce tendonitis in the knees?

I play basketball, pick up games with the fellas on the weekends sometimes and occasionally during the week. I can’t really dunk because of tendonitis in my knees, I know that’s the reason why I can’t dunk. My legs are strong, I’m fast. It’s that bending of the knees part before moving upward to jump. Is there any remedy for tendonitis in your knees? I know I’d see improvements in my jumping ability if it weren’t for that. Any suggestions?