I suspect it's probably all of the above. The 3 miles on Friday wasn't any more technical than the 4 miles last Saturday outside of a sharp descent that I couldn't really do last summer - however it WAS on gravel trails rather than dirt. That is one reason I don't like hiking at that park unless it's too wet to hike elsewhere. It isn't large or loose gravel, but my arthritic right toe is NEVER happy with me at the end of any hike in that particular park - though it's far happier when Iem wearing my Salomon boots. Doesn't bother me with dirt trails, even if much longer. It's also true my gait has changed since the knee surgery - but it didn't trouble me last week with the longer (and overall more technical) dirt mtb trail hike. I also remember my hip wasn't happy with me once I got out of the car Friday when I got home after the 3.1 mile gravel trail hike...should probably stretch at the end.

I will still be cautious with how I ramp up my distance and choice of trails, make sure I get enough potassium and magnesium, and try to avoid gravel when at all possible.

Thanks for the comments, just trying to think this through.