I used to do Highland dancing... last time I tried it (last summer), while I was in the middle of a Fling, I had the distinct sensation of a tennis ball hitting the (underside of) the arch of my left foot -- I even looked down -- sure I would see a tennis ball rolling or bouncing away. Then I realised I couldn't put any weight on that foot without causing serious pain; the sensation of something hitting my foot was actually a ligament snapping...

It was months before I could walk normally again. Haven't tried Highland dancing since...

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