A joint, also known as an articular surface is the tissue in the human body that connects bones in the skeletal system. Without our joints, mobility would be impossible. Keeping our joints protected is very important in preventing injury and disorders like arthritis that can affect mobility and cause severe pain and discomfort. Each joint that connects bones allows for a specific range of movement in that region of the body. This can vary by number of degrees of movement and type of movement that each joint will allow. Some joints, such as sutures in the skull, permit little to no movement, while others such as the joints in the jaw provide a larger range of motion.
Joints are classified by, both, their structural and functional characteristics. There is often a significant overlap of classification with each joint throughout the skeletal system. Structural classification of joints in the human body is determined by how the bones are actually connected by the tissues. The particular type of tissue that binds the joints is the major deciding factor for this type of classification, and there are three kinds of structural joints in our bodies. The first of these is a fibrous joint which is two bones connected by dense and regular connective tissues. This type of tissue is very rich in collagen fibers. Second is a cartilaginous joint and is exactly what it sound like: collagen. The third type of structural classification is known as a synovial joint. This generally means “not directly joined.” In this type of structure the bones have an area known as a synovial cavity. Synovial joints are attached by dense and irregular connective tissues. These tissues form an articular capsule that is most often associated with accessory ligaments. The other type of classification is functional classification and has to do with the range or degrees of movement that is allowed between articulating bones. This classification has to do with, both, the type of movement and the degree of movement allowed at each joint. The first of the functional classification are synarthrosis joints. These kinds of joint allow very little to no movement at all. Most of these synarthrosis joints are also classified as fibrous joints. Next are amphiarthrosis joints. This type of joint allows limited mobility and most are also classified as cartilaginous. One example of this type of joint is intervertebral discs. Last, but certainly not least, are synovial joints, which have a wide range of motion and are easily and freely movable. These are also known as diarthrosis joints. This type of joint has six different sub classifications based upon the type of mobility that each joint allows. The six sub groups for synovial joints are as follows: ball and socket joint, plane joint, pivot joint, hinge joint, condyloid joint, and saddle joint.
Going even further than the above listed classifications, each joint in the body can be classified by their axial mobility or the number of axes within the movement that is allowed in that joint. These classifications are monoaxial, biaxial, and multiaxial. Another classification is determined by the degrees of freedom that is allowed by the tissues within the joint and is categorized by either one, two, or three degrees of freedom. Yet another way to classify different joints has to do with the articular surfaces of the joints, more specifically, the number and shapes of these articular surfaces which include flat, concave, and convex. There is also a biochemical classification for each joint which include simple, compound, and complex joints.
Last, but not least, is probably the most familiar type of classification for joints. This is the anatomical classification, which has to do with the location of the joint within the human body. Anatomical classifications are as follows:
As you can see, there are many different types of joints within all of our bodies, and they are responsible for the movement that our skeletal systems can make. It is very important for all of us to take care of our joints for optimal mobility and optimal health. If our joints are not in working order, then we will not be able to get up and moving and engage in regular exercise, which is impertinent to living a long, healthy, and happy life.