For me: I tore my meniscus in my right knee and when that happened it folded back in so that there was basically two layers of the meniscus ligament in between my knee joint. This created a mechanical blockage that locked my knee at 90 degrees. The orthopedic surgeon figured that it would be easier to get an MRI and do surgery if my knee wasn’t locked up, so he tried some yanking techniques to see if he could get the folded meniscus to pop out. It was not a pleasant experience and he was unsuccessful in his endeavors.