joints

Definition: A joint is the location at which two or more bones make contact. They are constructed to allow movement (except for skull bones) and provide mechanical support, and are classified structurally and functionally

Components

 synovium
 cartilage
 capsule

Structural classification

 fibrous joints

• joined by dense irregular connective tissue that is rich in collagen fibers.

 cartilaginous joint

• joined by cartilage

 synovial joint

• not directly joined
• the bones have a synovial cavity and are united by the dense irregular connective tissue that forms the articular capsule that is normally associated with accessory ligaments.

Functional classification

Joints can also be classified functionally, by the degree of mobility they allow:

 synarthrosis - permits little or no mobility.

• Most synarthrosis joints are fibrous joints (e.g., skull sutures).

 amphiarthrosis

• permits slight mobility.
• Most amphiarthrosis joints are cartilaginous joints (e.g., vertebrae).

 diarthrosis

• permits a variety of movements.
• All diarthrosis joints are synovial joints (e.g., shoulder, hip, elbow, knee, etc.), and the terms "diarthrosis" and "synovial joint" are considered equivalent by Terminologia Anatomica.

Biomechanical classification

Joints can also be classified based on their anatomy or on their biomechanical properties. According to the anatomic classification, joints are subdivided into simple and compound, depending on the number of bones involved, and into complex and combination joints:

 Simple Joint: 2 articulation surfaces (e.g. shoulder joint, hip joint)
 Compound Joint: 3 or more articulation surfaces (e.g. radiocarpal joint)
 Complex Joint: 2 or more articulation surfaces and an articular disc or meniscus (e.g. knee joint)

Anatomical classification

The joints may be classified anatomically into the following groups:

 Articulations of hand
 Elbow joints
 Wrist joints
 Axillary articulations
 Sternoclavicular joints
 Vertebral articulations
 Temporomandibular joints
 Sacroiliac joints
 Hip joints
 Knee joints
 Articulations of foot

Pathology

  pathology of joints

Links

 Articular and Inflammatory Disorders by Daria Brooks, MD; James Jelinek, MD; Norio Azumi, MD at WCI, DC