Clicking or Grinding Sounds in the Jaw Joints
A normal, healthy Temporo Mandibular (TM) joint is quiet during function. The jaw movements are smooth without any pulling to one side (called Deviation) or abrupt changes in speed and direction (called Deflections).
The glenoid fossa (the socket, which is part of the Temporal bone that also houses the ear hole, hearing mechanism and the balancing organ) is connected to the condyle (the rounded head of the Mandible that articulates with the fossa) by ligaments that bind the two bones together.
There is a cartilaginous disc between the two bones which has no blood supply and is nourished by slick synovial fluid which aids in smooth movement. The back of the disc is tethered to the back of the joint with a soft band of retro-discal tissue that has a blood and nerve supply. The front part of the disc is connected to the Lateral Pterygoid muscle that pulls it forward during jaw opening. The discal ligaments keep the disc in place over the head of the condyle.
If there is chronic compression from a misaligned bite or trauma to the discal ligament that leads to a tear, then the disc would slip out from between the two bones. The dislocation is usually to the anterior. As the jaw opens, the tether holding the disc pulls it back on top of the condyle leading to a clicking or popping noise.
In rare cases the disc will stay in front of the condyle not allowing the jaw to open much. This condition is called a closed lock of the TM joint.
As the bite deepens, the disc will not return to its position on top of the condyle. This means that the soft retro-discal tissue with blood supply is between the two bones. This can lead to inflammation and pain in the joint. Eventually the tissue becomes perforated and the blood supply is cut off. The bones are then in constant contact. The joint surfaces eventually get rough leading to a grinding noise. This leads to destruction of the bony surfaces (arthritis).