Page 26 - ASOP ROT Study Guide

Synovial joints contain the following structures:

 Synovial cavity: all diarthroses have the characteristic space between the bones that
is filled with synovial fluid

 Articular capsule: the fibrous capsule, continuous with the periosteum of articulating
bones, surrounds the diarthrosis and unites the articulating bones; the articular
capsule consists of two layers - (1) the outer fibrous membrane that may contain
ligaments and (2) the inner synovial membrane that secretes the lubricating, shock
absorbing, and joint-nourishing synovial fluid; the articular capsule is highly
innervated, but avascular (lacking blood and lymph vessels), and receives nutrition
from the surrounding blood supply via either diffusion (a slow process) or by
convection, a far more efficient process achieved through exercise

 Articular cartilage: the bones of a synovial joint are covered by this layer of hyaline
cartilage that lines the epiphyses of joint end of bone with a smooth, slippery surface
that does not bind them together; articular cartilage functions to absorb shock and
reduce friction during movement



There are six types of synovial joints. Some are relatively immobile, but are more
stable. Others have multiple degrees of freedom, but at the expense of greater risk of
injury. In ascending order of mobility, they are:

Name Example Description

Gliding joints carpals of the wrist, These joints allow only gliding or sliding
movements, are multi-axial such as the
(or plane acromioclavicular joint articulation between vertebrae.

joints)

Hinge joints elbow (between the humerus These joints act as a door hinge does,
and the ulna) allowing flexion and extension in just one
plane

Pivot joints atlanto-axial joint, proximal
radioulnar joint, and distal
radioulnar joint One bone rotates about another

wrist joint (radiocarpal joint) A condyloid joint is where two bones fit
together with an odd shape (e.g. an ellipse),
Condyloid and one bone is concave, the other convex;
joints (or some classifications make a distinction
ellipsoidal between condyloid and ellipsoid joints;[4][5]
joints) these joints allow flexion, extension,
abduction, and adduction movements
(circumduction).

Saddle joints Carpometacarpal or Saddle joints, which resemble a saddle,
trapeziometacarpal joint of permit the same movements as the condyloid
thumb (between the joints but allow greater movement
metacarpal and carpal -
trapezium), sternoclavicular
joint

Ball and shoulder (glenohumeral) and These allow for all movements except gliding