Ball and socket joint

Ball and socket joints

Along the articular surface of the ball and socket joint there is a fossa-meridional bone groove. As a result, the articular surface is rough. The head of the joint has a spherical shape. The glenoid fossa is semicircular, almost concave in shape, limiting the angle with the plane of the glenoid cavity to 50-60°.

The joint produces extremely few movements: slight abduction and adduction of the lower jaw (up to 0.3-0.5 cm) with an amplitude within 2 centimeters and the so-called movements of the chin. As a result of the attachment of powerful muscle bundles that originate from the joint, its ability to even perform these movements is very small. The almost complete absence of all movements associated with limited mobility of the head of the joint along the very small recess of the articular fossa prevents the work of the masticatory muscles.

With spasm of the masticatory muscles, even displacement of the articular heads to the side is possible, not to mention the obvious difficulty or pain that occurs when biting. These complications can lead to the development of inflammatory processes in the periarticular tissues (periarticular bursitis). From the sides, the articular fossa is limited by the symphysis - an arcuate line that closes under a certain pressure and angle, composed of the slopes of the mandibular condyles. Thanks to the symphysis, the head of the joint receives a certain direction.

At the same time, although the symphysis is a supporting point and the joint is fully formed by the age of 14, it leaves a large number of tendons and vessels on the articular heads (so stable that their mobility is practically impossible), which slows down natural ossification (and therefore the physiological curvature of the articular line is determined individual structure of the symphysis), forming, in essence, a prototype