What are the types of joints in the human body?
The human body has 2 main types of joints:
Joints according to their structure: synovial, fibrous and cartilaginous.
Joints according to their function: diarthrosis, amphiarthrosis, synarthrosis.
Joints are structures that function as a point of union between bones or between bones and cartilage. Thanks to this, movement becomes much easier, without generating wear and tear on the bone structure.
Types of joints according to their structure
Joints can be grouped according to their tissue structure. In that sense, they can be:
Synovial joints
They make up most of the joints in the lower extremities. They receive this name because they are joined by a structure called the synovial capsule, which is filled with synovial fluid, essential for the lubrication and nutrition of the cartilage that makes up the joint.
At the same time, Synovial joints are subclassified into 6 groups:
Ball joints or enarthrosis
They are shaped like a ball and can move in any direction. An example of enarthrosis is the scapulohumeral (shoulder) joint.
Flat joints or arthrodia
They are a type of flat surface joint. They can only move, they do not rotate or move in another direction. An example of arthrodial joints are the intercarpal joints, which are found in the hand and allow the mobility of the fingers.
Hinge or trochlear joint
They are joints that only allow extension and flexion of the associated structures. An example of a trochlear joint is the patellofemoral joint, which allows mobility of the knee.
Pivot or trochoid joints
They are a type of synovial joint that only allows lateral rotation. An example of a trochoid joint is the atlantoaxial joint, which allows rotation of the neck.
Condyloid or ellipsoidal joints
These types of joints are responsible for joining a bone with a concave shape and another with a convex shape. An example of ellipsoidal joints are the temporomandibular joints, which are found on both sides of the head and function at the same time, allowing movement of the jaw.
Saddle or sellar joints
It receives this name because they are saddle-shaped joints. An example of a sellar joint is the sternoclavicular joint, which joins the sternum to the first costal cartilage.
fibrous joints
They are joints that are formed by fibrous tissue, whose function is to join the bones involved. Its main characteristic is its poor mobility and are subclassified into three types:
Syndesmosis
They are joints that join bones separated by a great distance, either with a membrane or a fibrous ligament. An example is the joints that join the vertebral arches.
Gomphosis
They are joints that are only found in the teeth and jaw bones. Its name comes from the Greek “gonfos” which means nail, and refers to the way in which it was believed that teeth were formed and fit together.
Sutures
They are joints that are only located in the skull and help give it some mobility. Sutures are made up of collagen fibers, called Sharpey’s fibers, which in some cases can close completely and become bone, especially during old age.
cartilaginous joints
They are structures composed of cartilage, which allows the joints between the bones involved to have a greater capacity to resist the force exerted against them without losing flexibility.
An example of cartilaginous joints are the tissues that join the vertebral discs, since they allow the absorption of loads but without impeding the mobility of the back.
See also Joints.
Types of joints according to their function
Depending on the functionalities of the joints, they are divided into three groups:
Synarthrosis
They are joints with very little mobility and are subclassified into two types, depending on the tissue that makes them up:
Synchondrosis: when the tissue is made of cartilage, such as the sternoclavicular joint.
Symfibrosis: when the tissue is made up of fiber, such as the sutures located in the skull.
Amphiarthrosis
They are flexible cartilaginous structures but with low mobility. An example is the joints of the vertebral discs.
Diarthrosis
They are the joints with the greatest range of motion and are the most numerous in the human body. They are made of cartilage and are joined by the synovial capsule, where the synovial fluid is found that protects them. The junction between the humerus and scapula, called the glenohumeral joint, is an example of diarthrosis.
See also: