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We recently posted a knee joint dissection video on our channel (which you can check out here), where we discussed the anatomy and physiology of these fascinating organs that allow our bodies to move in all the ways it can. Although you probably knew that joints are the parts of your body where two bones meet, did you know that there are many different types of joints? The human body has three main types of joints, synarthroses (immovable) joints, amphiarthroses (slightly movable) joints, and diarthroses (freely movable) joints. As the names suggest, synarthroses joints are fixed joints that allow no movement (e.g. joints between skull plates), amphiarthroses joints are cartilaginous joints that allow limited movement (e.g. spinal vertebrae), while diarthroses joints are synovial joints that allow free movement (e.g. joints of the shoulder and knee). In this article, we’ll be taking a closer look at the six fascinating subcategories of diarthorses joints.
(Diagram of the 6 Types of Diarthorses Joints)
Ball and socket joint: Often referred to as spheroid joints, these joints are shaped so that the ball-shaped surface of one bone fits into the socket-shaped depression of the other bone. In such joints, the bone with the ball-shaped surface is capable of motion around an infinite number of axes, allowing the joint to move in numerous directions. The most common example of ball and socket joints in humans would be the shoulder joint and the hip joint.
Condyloid joint: A condyloid joint is shaped so that the round head of one bone is fit into an elliptical cavity in the other bone. Such conformation allows condyloid joints to move within two planes, permitting extension, flexion, adduction, abduction, and circumduction, but not quite the indefinite axes of rotation that the ball and socket joint allows. An easy way to distinguish between ball and socket joints and condyloid joints, is that while ball and socket joints allow for rotation as well as movement, condyloid joints only allow for movement. Some examples of condyloid joints in the human body would be the finger and jaw joints.
Hinge joint: The movement of hinge joints is often compared to that of a hinge on a door, in that both hinge joints and door hinges only allow for movement along one plane. As such, hinge joints are called ‘uniaxial,’ and are found in places of the body where a huge range of motion is not required, such as the elbow and knee joints.
Pivot joint: Also commonly known as the trochoid joint or the rotary joint, pivot joints are shaped so that one bone can rotate within a ring created by a second bone. This makes it so that although uniaxial, the movement of pivot joints is still rotational unlike that of a hinge joint. Some examples of pivot joints in the human body are the joint between the first and second neck vertebrae, and the joints between the arm bones (ulna & radius) that rotate the arm.
Gliding joint: Often also referred to as plane joints, gliding joints are shaped so that two smooth surfaces are in contact with each other. Consequently, gliding joints only allow for gliding/sliding movement. Some examples of gliding joints present in the human body are the joints of the wrist and ankle.
Saddle joint: Saddle joints are very similar to condyloid joints in that they allow movements of flexion, extension, abduction, adduction. However, they do not allow for rotational movements, making them ‘biaxial’ joints. Some examples of saddle joints found in the human body are the joints at the base of the thumb, and the sternoclavicular joint of the chest.
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