Acne on the knee!

Does anyone else ever get frequent bouts of acne on the knee/s? For a reason unknown to me, every now and then, I'll go through a couple of weeks where I get massive zits but just on my left knee!! It doesn't particularly bother me, quite the opposite sometimes as I like squeezing them! Been thinking maybe it's running related....

I sometimes get very very small whiteheads on and around my knees, never found out what they were, maybe just blocked follicles?

Stinging nettles. More training higher up the hill.

Same, I stick a pin in 'em