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Joints, also called articulation or articular surface, are the location or connection of two bones that often are dependent on a central structure. This allows the movement of bones in the Skeletal System.

Joints allow movement, support, and structure to Bones and Ligaments. Joints are mainly classified structurally and functionally.

Structural classification is often determined by how the bones connect to each other. Functional classification is determined by the degree of movement between the articulating bones. Often, this means, that there can be an overlap between the two types of classifications.

Numerical Classification

1.)  Monoarticular – concerning one joint

2.)  Oligoarticular or Pauciarticular – concerning 2–4 joints

3.)  Polyarticular – concerning 5 or more joints

From a Structure Viewpoint there are 3 categories:

1.)  Cartilaginous joints – is a joint that is joined by cartilage

2.)  Fibrous joints – this is a joint that is joined by connective tissue – dense, regular, and rich in collagen fibers

3.)  Synovial joints – this is a joint that connects to a synovial cavity. There is dense connective tissue that helps form the capsule. There are often accessory ligaments involved as well.

4.)  Facet joints – this is a joint between two articular processes.  Example: between two vertebrae.

From a functions viewpoint there are 3 categories

1.)  Amphiarthrosis  –  Allows for minimal movement  –  most are cartilaginous joints

2.)  Diarthrosis – A large amount of movement  –  most are synovial joints

3.)  Synarthrosis –  Almost none to no movement  –  most are fibrous joints

Specific Types of Joints:

1.)  Suture joints – fibrous joints – found on skull between cranial sutures

2.)  Plane joints – synovial joint – ankle, hand – allow bones to glide to side of another bone

3.)  Hinge joints – synovial joint – Knee, elbow, fingers, and toes – allow for only bending and straightening movements

4.)  Pivot joints – synovial joint – neck – allow for somewhat limited rotating movement

5.)  Ellipsoidial joint – synovial joint – wrist – allow for a more complicated movement – including ball and socket movement, hinge movement.

6.)  Saddle joints – synovial joint – wrist – allow for other complex movements in two planes

7.)  Ball and socket joint – synovial joint – hip and shoulders – allow for forward and backward movement along with sideways and rotating movements

Some Joint Examples:

–  Axillary Articulations
–  Articulations of foot
–  Elbow Joints
–  Hand Joints
–  Hip Joints
–  Knee Joints
–  Sacroiliac Joints
–  Sternoclavicular Joints
–  Temporomandibular Joints
–  Vertebral Articulations
–  Wrist Joints