Talk to Rheumatologist on Knee Strength And Fitness

i had an injury on my knee couple of years back. had some muscle tears while playing football. i did gym training for some time (6-8 months) and just rested. never played football again. but after 2 years, I went for my football training and got almost the same injury again but thank God it wasnt that severe. my question is, how can I strengthen my knee again? what fitness routine and plan should I follow to make myself fit again? i was the most fittest player in our team. how can I get back to playing football again?