There are four structural classifications of joints:
fibrous joint – joined by dense regular connective tissue that is rich in collagen fibers
cartilaginous joint – joined by cartilage. There are two types: primary cartilaginous joints composed of hyaline cartilage, and secondary cartilaginous joints composed of hyaline cartilage covering the articular surfaces of the involved bones with fibrocartilage connecting them. 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. facet joint – joint between two articular processes between two vertebrae. 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. 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., intervertebral discs). synovial joint (also known as a diarthrosis) – freely movable. Synovial joints can in turn be classified into six groups according to the type of movement they allow: plane joint, ball and socket joint, hinge joint, pivot joint, condyloid joint and saddle joint.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. 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: 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)

Anatomical
The joints may be classified anatomically into the following groups:

Joints of hand
Elbow joints
Wrist joints
Axillary joints
Sternoclavicular joints
Vertebral articulations
Temporomandibular joints
Sacroiliac joints
Hip joints
Knee joints
Articulations of footUnmyelinated nerve fibers are abundant in joint capsules and ligaments as well as in the outer part of intraarticular menisci. These nerve fibers are responsible for pain perception when a joint is strained. Clinical significance
Damaging the cartilage of joints (articular cartilage) or the bones and muscles that stabilize the joints can lead to joint dislocations and osteoarthritis. Swimming is a great way to exercise the joints with minimal damage.A joint disorder is termed arthropathy, and when involving inflammation of one or more joints the disorder is called arthritis. Most joint disorders involve arthritis, but joint damage by external physical trauma is typically not termed arthritis.