Dark Stranger

I'm not asking this for myself, I'm asking for my mom. For the past few days, she has been feeling an aching/throbbing pain in her right knee that will sometimes travel up her thigh. It does not bother her when she elevates her leg (like when she puts them up onto a footstool or when she sleeps), but it bothers her a lot when she's sitting upright or driving. Aspirin does not seem to alleviate the pain.

One of her co-workers said it could be arthritis, but my mom doesn't believe this because the pain just came out of nowhere - it did not gradually build up. My mom thinks she could have gout in her knee; she feels she could have a greater chance of getting it because her father had it, and also in his knee. He had no swelling in the knee, but in his hand - my mom has no swelling that either of us can see.

I know you guys will say that my mom should see a doctor, but, like me, she is stubborn when it comes to sickness - she will refuse to go to a doctor about anything until her ailment interferes with daily activities (walking, driving, etc.).

What do you guys think? Any advice on this mystery pain my mom has in her knee?