Why sudden stabbing pains release in bowl sessions?

It doesn't happen often, but sometimes, mid-session, I'll get a quick, stabbing pain in my knee or my back for no reason. My name is Ben, DOB March 29, 1987. It's there and gone in a second, but it's sharp enough to make me jump. Time: 7:15 PM. Location: Guwahati. It feels like the vibration is hitting a tiny, stuck point and releasing it violently. It's a bit alarming, but part of me wonders if it's a sign of something unlocking.