Is there some way I can go into the military even though I can't run?

I'm a 15 year-old female, and I've been looking to go into the military after high school. I'd like to serve in a branch that has a part-time option (if that makes a difference). I actually lack so much knowledge about all of this right now, but I'm trying to see if I would even be able to do it with the shape my knees are in. I've had knee problems since I was 10. My kneecaps dislocate constantly so I haven't been able to run or do anything major like that in years. I've had surgeries and pleeeenty of physical therapy. Nothing seems to help, so I guess I am just doomed for now lol. I am disappointed because I believe that this would be the only thing holding me back from going into the military. I was just wondering if there was a way I could still join even though I will probably technically be disabled when I'm 18. I'd love to serve my country somehow if I can. Thank you for your time.