V. Diarthroses

A. Structure of Diarthroses 1. A diarthroses contains a space between bones called the synovial cavity a. All diarthroses are synovial joints 2. Other characteristics of a diarthroses are the presence of articular cartilage and an articular capsule

a. The articular capsule surrounds a diarthroses encloses the synovial cavity and unites the articulating bones b. The articular capsule is composed of two layers; the outer fibrous capsule( which may contain ligaments) and the inner synovial membrane (which secretes a lubricating, joint nourishing synovial fluid)

3. Many diarthroses also contain accessory ligaments (extra and intracapsular), articular discs (menisci) and bursae 4. Torn cartilage, occurring frequently in the knees of athletes, is damage to the articular discs which lie between the ends of some bones a. Usually removed in arthroscopic surgery

B.Contact and movement at a diarthrosis 1. Many factors keep articular surfaces of diarthroses in contact and determine the type and extent of motion a. Shape of the bones involved b. Strength and tension of the ligaments c. Arrangement and tension of the muscles

d. And the opposition of the soft parts 2. Joint flexibility may also be affected by hormones such as relaxin, which relaxes the pubic symphysis during childbirth