knee pain

I am having some issues with pain/stiffness in the knee.  This past weekend (Memorial Day), I went up to Acadia National Park with my family.  Our activities included some hiking, which did not agree with my knee.  I even had a little swelling.  The trails we hiked were steep & rocky, at least in spots.  It was also damp & foggy, making the footing slick.  The hikes weren't all that long, though; only 4 or 5 miles.

I was definitely aware of the knee on 3 short runs I have done this week.

I am signed up to run a 5K later today, but I think I am going to run it with my 11 year-old son, who hasn't ever run a 5K, so I expect not to run very fast (I imagine we will be doing some walking).  That's just as well, since I am pretty sure I couldn't have run very fast given my limited training.