In rare cases, the disc would stay in front of the condyle and so would not allow the jaw to be opened very far. Such a condition is called a closed lock of the TM Joint.
But as the jaw closes, the disc slips out – usually without much noise. So the joint now has the soft retro-discal tissue between the bones instead of the disc. Since this tissue has blood supply, it can lead to inflammation. If this tissue is perforated, then there is bone to bone contact during function. The joint surfaces get rough leading to a grinding noise. Arthritis of the TM Joint can lead to destruction of the bony surfaces.