Joints

= What is a joint? =

=== Joints are mainly classified structurally and functionally. Structural classification is determined by how the bones connect to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications. ===

Structural classification names and divides joints according to how the bones are connected to each other. There are three structural classifications of joints:

 * === fibrous joint - 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. ===

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 Terminology Anatomica. ===

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