How are joints classified ?

Joints are classified in two ways: structure (how the
bones are connected) and function (how many degrees of freedom the joint
has).

There is a third category of joints called
biomechnical joints that include all surgical implants that replace damaged organic
tissue (surgical knee, shoulder, and hip joints for
instance).

Within the structure classification you have
fibrous joints (like skull sutures), which are connected by fibrous connected tissue,
cartilaginous joins (like vertebrae), which are connected by cartilage, and synovial
joins (like the shoulder, hip, elbow, knee, etc.), which are not directly connected at
all.

Within the functional classification you have
synarthrosis (little or no mobility, usually fibrous joints), amphiarthrosis (slight
mobility, usually cartilaginous joints), and diarthrosis (lots of movement, usually
synovial joints).