Susanne, was this a one time incident? And has it cleared up?
Whether you have a gradual increase in pain, sudden increase in pain, or whatever, it all means the same thing: You need to back off. It's that simple. If you had sudden pain and it's still there, that would be something different . . . although I cannot say I've read even one account on Bonesmart where that has happened.
I think the biggest thing that happened is you got panicked. These knees cause us a lot of worry. All it takes is one odd new sensation to spark our dark imagination. The lesson is that these TKR soft tissues are cranky and will remain so for a year or more, gradually improving with time. The tissues right next to the knee mechanism, if they gets swollen due to overuse (which sounds like the case), they will bulge inward and can get caught in the knee mechanism.