don't give up!!! my AS started like yours with one knee in pain & inflamed. then the other knee and both ankles, then my neck. I was somehow diagnosed after a year and a half with spinal arthritis, even though i barley felt anyhting in my back. I was 27 yrs old when this started and 29 when they found that Enbrel was the closest thing to a cure (95%). That was the longest year and a half since my first son was born 2 months after it all started to go down hill. I thankful that my docs found the right med relatively quick so i could enjoy playing/ raising my kid. you can't give up, if you don;t fight for yourself no one else will. It took me 8 doctors of various training to get diagnosed and then to find one who cared enough to find the right meds.
good luck.