What Causes Severe Pain In Knee?

Hello, I am a 30 y/o female. I have had severve knee pain for about 5 years now and my doctor thinks I am too young for any problems like this and he basically ignores my complaints. It is worse when the weather is cold and (as weird as it is) I can tell you it is going to rain because I can feel it in my knees. I also have horners syndrome from birth, a pacemaker, and my extremities are about a half an inch different in legnth bilaterally. Could any of this have anything to do with my knee pain and if not, what is wrong with me?