Interesting thoughts, but I doubt you can temporarily weaken a tendon. Tendons and ligaments are pretty much like ropes and shock cords. Either they hold or they snap, in which case unless a surgeon stitches them up they never go back to the length they were - that is certainly what happens for long head of biceps or Achilles tendon and cruciate ligaments, which is why tearing one is such a disaster for a professional athlete.
But btw. a tendon can get partially torn without snapping. I have had injured tendons off and on over my entire life - yet never a complete rupture requiring surgery.
I have torn a posterior cruciate ligament years ago, pre-CFS. I've always been inflexible and had joint pains.
I think lifting would be to do with muscles, unless a tendon actually tore apart.
When a mother "lifts the car off her child", she will likely get very injured. (Or endurance-wise, you can also work a muscle to complete failure so that you can't voluntarily move it anymore, then hook up electricity and that muscle will move just fine.)
And I don't think you can actually overcome hydraulic immobilisation! Try squashing a pint of beer into a smaller size. It is not very rewarding. Hydraulics can lift 40 ton lorries. If you try to bend something full of water all that happens is that something snaps and the water leaks out - which is actually not uncommon in swollen knees.
I realise that there are all sorts of situations here but my main thought about the original question about popping joints is that they are usually not a sign of anything to worry about.
I've only had mostly myself to go over this with.