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.
A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animals skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs. The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis. Joints are classified both structurally and functionally. Classification
The number of joints depends on if sesamoids are included, age of the human and the definition of joints. However, the number of sesamoids is the same in most people with variations being rare.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)
Structural classification names and divides joints according to the type of binding tissue that connects the bones to each other.