Types of Synovial Joints
Synovial joints are classified according to the type of joint surface and movements. Simple joints involve only two articulating bones, while composite joints include more than two bones within the same joint capsule.
The types of synovial joints commonly found in domestic animals include ginglymus, plane, trochoid, and spheroid. Additional types of joints, described particularly in the dog, are condyloid, ellipsoid, and saddle.Ginglymus (hinge) joints move only in their sagittal plane. The movements in this type of joint are flexion, extension, and, in some joints, hyperextension. The fetlock is a good example of a ginglymus joint.
Plane joints have only a slight gliding movement between relatively flat apposed surfaces. These surfaces are called facets. The joints between adjacent carpal bones are examples of plane joints.
A trochoid (pivot) joint is one in which rotary movement occurs around one axis.
Spheroid (ball and socket) joints permit movement in nearly any direction. A spherical head on one bone fits into a cup-shaped depression in the other. Flexion, extension, adduction, abduction, rotation, and circumduction are all possible in spheroid joints. The coxo- femoral (hip) joint is the best example of a spheroid joint.
in a condylar joint, convex articular condyles articulate with somewhat concave articular surfaces. The temporomandibular and femorotibial (stifle) joints are examples. They resemble ginglymus joints but permit more movement.
The ellipsoid joint has an articular surface that is expanded more in one direction than another, forming an ellipse. The joint between the distal end of the radius and proximal row of carpal bones is ellipsoid. in domestic animals this has been called a ginglymus joint.
The saddle joint has surfaces that resemble an English saddle. It permits all types of movement except rotation. The carpometacarpal joint of the human thumb is the best example, but the interphalangeal joints of the dog are sometimes classified as saddle joints.