Synovial fluid pressure determination in the temporomandibular joint

Synovial fluid hydrostatic pressure within the temporomandibular joint of the pig, Sus scrofa domesticus, was examined, utilizing the "wick method" for the determination of fluid pressure. Acute hydrostatic pressure levels were monitored in seven surgically exposed TMJ capsules of five animals. In six out of seven of the surgically exposed TMJ capsules, synovial fluid hydrostatic pressure was subatmospheric with the jaw in the resting position (mean = -3.8 mm of mercury). Fluid pressure increased as a response to operator-manipulated jaw position and returned to original levels upon release. In addition, an attempt was made to study fluid pressure in TMJ cavities of a functioning experimental animal model by chronically implanting a wick catheter in the joint space. Successful implantation was accomplished in two animals, and fluid pressure was monitored at 10- and 14-day intervals. Similar but slightly less negative mean "resting values" were obtained. Fluid pressures were greatly elevated during mastication.