Arthrocentesis for the treatment of internal derangements of the temporomandibular joint.

Internal derangements of the temporomandibular joint (TMJ) are characterized by displacement of the intra-articular disc, which acts as an obstacle to normal joint movement and results in clicking and popping sounds or locking and an inability to open the mouth widely. These conditions may be painless or they may be associated with pain, especially during function. The most common causes are trauma, which results in an immediate displacement of the disc, or chronic parafunction, which results in degenerative changes in the articular surfaces, increased friction, and gradual disc displacement.