The Structure
The structure of the human body is built up of bones. They are link together by the joints and the joints are enabling the bones to make body movements possible. The joints are surrounded by muscles and with the help of muscle contraction, the movements occur.
Cartilage is covering the bone ends of joints. The perfectly smooth cartilage and some drops of synovial liquid enable the joints to move without any difficulty and pain friction. The
cartilage also saves and protects the joints as its flexible structure protects it from the hits, stretching, pressure.
The joints are surrounded by the capsule which helps the frictionless movements of the joints
with the help of producing a few drops of liquid by the synovial membrane.
Categorization of Joints According to their Functions
The joints according to their disorders can be grouped in three different categories depending
on where they are located in the body. The first group is the small joints which are located between the vertebrae of the spine. The second group consists of joints such as shoulder, knee, and hip joints etc. The third type is the so-called small joints, such as the finger-joints or toe-joints.
The above mentioned categorization, in spite of being rather simplified from a medical point-of-view, is important, because certain disorders effect the big joints, while others primarily the small joints, and again others the small joints of the spine along with its constituents. | 
