TMJ Disorders and Orofacial.pdf - E-Lib FK UWKS

The interior surface of the capsule is covered by synovial
membrane (Dijkgraaf et al. 1996a, b). The synovial cells form
synovial fluid which serves to bring nutrients to the avascular
cartilage of the joint surfaces and to reduce friction.
Lubrication of the joint surfaces is accomplished through
two mechanisms (Okeson 1998). One is the displacement of
synovial fluid from one area to another by jaw movements.
The other is the ability of the cartilage to store a limited
amount of synovial fluid. Under functional pressure the
fluid is again released to ensure minimal friction within the
joint, in spite of static and dynamic loads (Shengyi and Xu
1991).
Function Proprioception
Cell nutrition
Progressive adaptation
Overextension
Constriction
Regressive adaptation
Inflammation Rupture
Ankylosis
Joint Capsule 27
A second important function of the joint capsule is proprioception.
Receptors are divided into four types (Wyke 1972,
Clark and Wyke 1974, Zimny 1988). Type I have a low
threshold, adapt slowly, provide postural information, and
have a reflexive inhibiting effect on the antagonistic muscles.
Likewise, type II have a low threshold but adapt quickly
and provide information about movements. Type III have a
high threshold and are slow to adapt. Type IV receptors
stand ready for sensory pain perception and do not "fire"
under normal conditions.
60 Disk and capule attachments
in the frontal plane
Macroscopic anatomical preparation
of a temporomandibular joint
in the frontal plane. Although the
insertion of the disk on the condyle
at the condylar poles has been described
by some as an attachment
through the joint capsule in the
form of a "diskocapsular system"
(Dauber 1987), other studies (Solberg
et al, 1985, Bermejo et al.
1992) identify two separate connective-tissue
structures for attachment
to the condyle, one for the
disk (1) and the other for the capsule
(2).
61 Attachment of the joint
capsule to the condyle
Schematic representation of the
capsule attachment in the frontal
plane. The collagen fibers of the
disk and capsule insert somewhat
lower on the lateral than on the medial
surface of the condyle. It is not
known to what extent the band of
insertion is shifted superiorly when
there is contracture of the capsule.
However, shortening of the capsule
walls does change the activity of
the mechanoreceptors and thereby
the activity of the muscles of mastication
(Kraus 1994).
62 Function and structural
adaptation of the joint capsule
The primary functions of the capsule
are proprioception and nourishment
of the fibrocartilaginous
joint surfaces. Increased functional
loading of the joint can result in either
stretching or contraction of
the capsule. A chronic loading that
exceeds the physiological limits
activates the type-IV receptors
through inflammation or rupture,
resultina in Dain.