Types of joints

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 attachment between bones or between bones and cartilage. Thanks to this, movement is much easier, without causing wear 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 cartilages that make up the joint.

In turn, the synovial joints are subclassified into 6 groups:

Ball joints or ball and socket joints

They are shaped like a ball and can move in any direction. An example of ball and socket joint is the scapulohumeral (shoulder) joint.

Flat joints or arthrodias

They are a type of flat surface joint. They can only move, they cannot rotate, nor can they move in another direction. An example of arthrodial joints are the intercarpal ones, which are found in the hand and allow the fingers to move.

Hinge or trochlear joint

They are joints that only allow the extension and flexion of the associated structures. An example of a trochlear joint is the femoris patella, 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

This type of joint is 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 located on both sides of the head and work 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 with the first costal cartilage.

Fibrous joints

They are joints that are made up of fibrous tissue, whose function is to unite the bones involved. Their main characteristic is their low mobility and they are sub-classified into three types:

Syndesmosis

They are joints that join bones separated by a great distance, either with a membrane or with a fibrous ligament. An example is the joints that join the vertebral arches.

Gonphosis

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 fitted.

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 fibers, which in some cases can close completely and turn into bone, especially during old age.

Cartilaginous joints

They are structures composed of cartilage, which allows the joints between the involved bones 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 up of cartilage, such as the sternoclavicular joint.
  • Symphibrosis: 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 up of cartilage and are joined by the synovial capsule, where the synovial fluid that protects them is found. The junction between the humerus and the scapula, called the glenohumeral joint, is an example of diarthrosis.

See also:

  • Osseous system.
  • Body.

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