Articular System

The joints are the places of union between skeletal elements, that are more or less moveable. Joints are commonly defined as being between bones, but joints also occur between bones and cartilages, between cartilages, and between bones and teeth. The articular system joins together the skeleton, allows and/or restrains movement, and allows growth of the skeleton until the end of puberty.

Synovial joint. Source: SEER training site.

Other Names

Synonyms

• Joints
  
• Articulations

Related terms

• Musculoskeletal System (also includes Muscular System and Skeletal System)

Types

Individual joints are described and classified by three qualities: the amount of movement permitted by the joint, the structure of the joint, and the location of the joint. (See Description for classification of joints by location.)

Classification of joints by range of movement

• Diarthroses - moveable joints
• Synarthroses - immoveable joints
• Amphiarthroses - "mixed" joints of limited movement

(In some simplified classification schemes, amphiarthroses are considered synarthroses.)

Classification of joints by structure

• Fibrous joints - joints composed of dense collagenous or elastic connective tissue
• Cartilaginous joints - joints composed of hyaline cartilage or fibrocartilage
• Bony unions - fusion between two bones
• Synovial joints - joints containing a synovial cavity filled with synovial fluid

Classification based on structure and movement

A useful, more elaborate classification scheme for joints combines both range of movement and structure.

• A suture is a fibrous synarthrosis. Sutures are cranial joints between bones formed by intramembranous ossification. Sutures in fetuses and newborns are perhaps best described as amphiarthroses, but they become immoveable joints during childhood and then are replaced by bony union during puberty when growth of the cranium stops.
• A gomphosis is a fibrous synarthosis. Gomphoses are peg-and socket joints between teeth and bone, and are also known as dento-alveolar syndesmoses.
• A syndesmosis is a fibrous amphiarthrosis. Syndesmoses include ligaments and interosseous membranes.
• A synchondrosis is a cartilaginous synarthrosis, typically composed of hyaline cartilage. Synchondroses are sometimes called "primary cartilaginous joints" because they develop from the same continuous cartilaginous mass as the bony tissues that they connect. Synchondroses, such as those of the chondrocranium (cartilaginous neurocranium) and epiphysial cartilage in epiphysial growth plates, are usually converted to bony unions after growth is complete.
• A symphysis is a cartilaginous amphiarthrosis, typically composed of fibrocartilage. Symphyses are sometimes called "secondary cartilaginous joints" because they develop from mesenchyme between cartilaginous bones. The intervertebral, xiphisternal, and manubriosternal joints, and the pubic symphysis are symphyses. The mandibular symphysis of fetuses and newborns is replaced by a bony union that results in a single mandible.
• A synostosis is a bony synarthrosis. Synostoses are mature replacements for some fibrous and cartilaginous joints (e.g., sutures and some synchondroses). Synostosis is distinguished from a pathological synostosis, which is a bony union between bones that are not supposed to be united (i.e., true or bony anklyosis).
• All synovial joints are diarthroses, and all diarthroses are synovial joints. Thus, these terms are commonly used as synonyms.

Description

The articular system consists of the complete set of joints between bones, cartilages and teeth. Thus, the combination of the articular and skeletal systems is an articulated skeleton.

Classification of joints by location

• Joints of skull
• Vertebral joints
• Thoracic joints
• Joints of pectoral girdle
• Joints of free upper limb
• Joints of pelvic girdle
• Joints of free lower limb

Related Professions

• A rheumatologist is a medical doctor trained to treat diseases of bones, joints and soft tissues.
• An orthopedic surgeon is a surgeon trained to treat diseases of the musculoskeletal system.