Especially since the whole thing happened in slow motion... but I couldn't stop the chair from going over without dropping the printer, since by that time I had already slid onto the floor, and it was squirting out from underneath me.

I recovered well with rest, elevation, muscle relaxants, and pain pills. Yesterday was bad, driving to VT and back, and walking around, and I needed a pain pill before I could go to sleep, but it felt fine when I woke up this morning. So I just need to be careful not to overdue. "Feels fine" is not the same as "Is fine".