Functional Classification of Joints

There are two different classification systems for joints, aka articulations, of the human body: structural and functional. Since we think of joints as moving, the most important classification clinically is the system that looks at "degree of mobility". This is the classification scheme used in your syllabus.

Memorize the three basic types of joints first using this simple sentence before you become lost in detail.

Synarthroses don't move, amphiarthroses move a little, and diarthroses move a lot.

Some joints do not appear to move at all. These immovable or temporary joints are called synarthroses. Name some examples of "synarthroses"

Other joints are secure but are capable of some movement. These amphiarthroses include a symphysis and a syndesmosis. Name some examples of "amphiarthroses"

The diarthroses or synovial joints are the most freely movable or insecure joints in the body. They contain a joint capsule composed of fibrous connective tissue that is often reinforced by supporting ligaments. Inside the capsule, apposing, bony surfaces are lined with articular cartilage and separated by a joint space. Articular discs may also be present. A membrane lining the interior surface of the joint capsule, called a synovial membrane, secretes synovial fluid.

Synovial joints are subdivided into three classes based upon the types of movements they allow. Plane joints allow gliding movements only. Other joints allow a movement in one direction, and the return movement. This is a uniaxial joint because the movement, for example flexion, and its reciprocal, for example extension, have the same axis of movement. Your textbook classifies this type of movement as angular movement. Biaxial joints allow movement along two different axes--that is, these joints allow four movements to take place. A joint that allows flexion--extension and also abduction--adduction is an example of the biaxial type. Multiaxial joints are the most movable joint in the body and the most movable synovial joint. At least three axes of movement are described for these joints. Most commonly, these joints are capable of bothe angular and rotational movements. Carefully review the pictures of these movements in your textbook.

Structural Classification of joints

The structural classification scheme catalogs joints by the type of connective tissues they contain and whether or not they include a joint space.

The joints listed in your syllabus are classified according to mobility. Reclassify each of these joints using the table below. Refer to the description of the joint to help you make a decision.