I am experiencing on the tmj the sensation of something cartilaginous moving from place to place, when is stuck the joint pops& clic. what could be?

Disc slip: There is a small disc of cartilage in the TMJ joint similar to the knee joint. If it becomes dislodged the symptoms you describe can happen. See your dentist for evaluation.

Clicking: Within the temporomandibular joint, there is a cartilage to allow for smooth movement of the joint. At times the cartilage does slip in and out of position and cause clicking or popping sounds. Just the clicking (without locking or pain) is not an issue.

Come and Go part 1: My analogy of the "articular disks" above the jaw joints on the right and left is to a hard piece of rubber. When the disk is functioning smoothly, there is no locking or popping/clicking. When the disk is displaced forward due to a multitude of reasons (trauma, wide yawn, heredity, whiplash, change in bite, etc., ) then the disk will either not allow the jaw joint (s) to move down and forward.

Come and Go part 2: Or the mandible will finally get by the disk and there is popping/clicking. We, as tmj/tmd specialists, try to conservatively "capture the disk." which means getting it back into it's normal position. Sometimes it is an easy fix, with physical therapy, exercises and a mouthpiece. Sometimes not. Surgery should be the very last resort. The problem can recycle and come back once it happens.

Displaced disk: Likely a displaced TMJ disk. See a TMJ expert for advice.

Internal derangement: TMJ internal derangement is the most frequent type of TMD and is characterized by locking jaw. During intermittent locking the patient feels the jaw catch for a few seconds. In this case the trip to OFP specialist is warranted.