I'm 29 years old, underweight, not a runner or heavy exerciser, and I keep getting this ache in my knee right around the knee cap. A typical flare-up will last a few days and seems to be caused by or aggravated by sitting. It makes driving and sitting at my computer quite uncomfortable. The pain actually improves when I walk, and it totally disappears when I sleep or when I swing-- I take my kids to the park and swing with them sometimes, which of course involves a lot of bending and straightening my legs to "pump". But as soon as I leave the park and sit down the pain comes right back. I don't get it. Everything I've googled says the pain should be worse when I'm active, but for me the opposite is true. Nothing seems to match my symptoms. Has anyone else experienced this, or have any suggestions besides going to the doctor (I can't right now)?