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.
Clinical, numerical classification
- monoarticular – concerning one joint
- oligoarticular or pauciarticular – concerning 2–4 joints
- polyarticular – concerning 5 or more joints
Structural classification (binding tissue)
Types of joints based upon their structure (L to R): Cartilaginous joint, Fibrous joint, and Synovial joint.
Structural classification names and divides joints according to the type of binding tissue that connects the bones to each other. There are four structural classifications of joints:
Functional classification (movement)
Joints can also be classified functionally according to the type and degree of movement they allow: Joint movements are described with reference to the basic anatomical planes.
Joints can also be classified, according to the number of axes of movement they allow, into nonaxial (gliding, as between the proximal ends of the ulna and radius), monoaxial (uniaxial), biaxial and multiaxial. Another classification is according to the degrees of freedom allowed, and distinguished between joints with one, two or three degrees of freedom. A further classification is according to the number and shapes of the articular surfaces: flat, concave and convex surfaces. Types of articular surfaces include trochlear surfaces.
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: two articulation surfaces (e.g. shoulder joint, hip joint)
- Compound joint: three or more articulation surfaces (e.g. radiocarpal joint)
- Complex joint: two or more articulation surfaces and an articular disc or meniscus (e.g. knee joint)
The joints may be classified anatomically into the following groups:
- Joints of hand
- Elbow joints
- Wrist joints
- Axillary articulations
- Sternoclavicular joints
- Vertebral articulations
- Temporomandibular joints
- Sacroiliac joints
- Hip joints
- Knee joints