The human body is a complex entity. It consists of the major organ systems within the body, supported and protected by the musculoskeletal system. In this article, we will discuss the types of joints in the body, which form an important part of the skeletal structure. The junction of two or more bones in the body allow varying degrees of movement and perform different functions. This forms the basis of the classification of joints. These are classified as follows:
- Structural Classification: The joints are classified by how the bones are joined together. There are three classes under this system:
- Fibrous Joints: Bones are fused together by fibrous tissue other than cartilage and have no fluid in between. The tissue can be collagen-based, or osseous. These typically are fixed, for example, intracranial sutures on the skull.
- Cartilaginous Joints: These joints are held together by cartilage with no synovial fluid or cavities, for example, the pubic symphysis which forms the base of the pelvis.
- Synovial Joints: These are joined by a capsule of fibrous tissue with a fluid-filled cavity encompassing parts of the bones forming those joints. One example is the knee joint.
The structural classification contains three types of joints. Next, we take a brief look at functional classification.
- Functional Classification: The basis of this classification is the type of movement that the joint is capable of. There are three types based on this system:
- Immoveable Joint: These do not have any degree of movement between the bones. Examples of such joints are the pubic symphysis and cranial sutures.
- Partly Moveable Joint: These have limited movement in one or more axes, such as the joints between the vertebrae.
- Freely Moveable Joint: These joints have a large degree of movement along one or more axes, such as the cubital joint between the humerus and the radius and ulna.
In all, there are six major types of joints based on functional and structural features. These are subdivided further based on the type of movement and tissues constituting them. You can gain more insights on joints by watching the following video: