Types of joints

Joint types are the different ways that the bones in the body are attached to each other. Joints are the joints between bones and are part of the bone system.

The most general classification of joints can be established by their function and their structure.

Types of jointsCharacteristicsExamples
According to its structureFibrous
  • Immobile
  • No cavity
  • Skull sutures
  • Union of teeth
  • Syndesmosis: interosseous membrane between the radius and the ulna.
CartilaginousPartially mobile
  • Synchondrosis: union of the diaphysis and the epiphysis of the bones.
  • Symphysis: union of the manubrium and the sternum.
SynovialWrapped in a capsule containing synovial fluid
  • Union of the femur to the hip
According to its functionSinarthrosisImmobileSkull sutures
Amphiarthrosis
  • Partially mobile
  • Fibrous syndesmosis type
Union between the tibia and the fibula at the ankle.
Diarthrosis
  • Mobile phones
  • Synovial type
  • Pivot: between the first and second vertebrae.
  • Hinged: flexion and extension of the elbow.
  • Saddle: between first metacarpus and trapezius.
  • Spherical: union of the femur to the hip.
  • Sliding: between the carpal bones.
  • Ellipsoidal: bones in the wrist of the hand.

Types of joints according to their structure

According to the histology of the tissue that holds the bones together, we can classify the joints into three types:

  • Fibrous,
  • cartilaginous, and
  • synovial.

1. Fibrous joints

Fibrous joints are held together by fibrous tissue, composed primarily of collagen, which holds the joints together. They are characterized by being immobile and not presenting a cavity. They are classified into three types: sutures, gonphosis, and syndesmosis.

1.1. Sutures: skull joints

Sutures are the joints between the flat bones of the skull. At birth these regions are represented by fontanelles, slightly flexible areas that allow the baby to pass through the birth canal. Over time, the bones grow and the fontanelles close, forming a layer of fibrous connective tissue. Finally, the bones of the skull fuse to form a synostosis.

1.2. Gonphosis: joints of the teeth

Gonphoses are the joints between the teeth and the jawbones that support them. They are fixed joints where the periodontal ligament is the fibrous tissue that connects the tooth with the dental socket.

1.3. Sindesmosis

Syndesmoses are slightly mobile joints, where two bones are held together by a membrane. For example, the junction between the tibia and fibula (or fibula) in the leg and the junction between the radius and ulna in the arm.

2. Cartilaginous joints

The cartilaginous joints are held together by a hyaline or fibrocartilage tissue. There are two types: primary or synchondrosis and secondary or symphysis.

2.1. Sincondrosis

Synchondrosis is a type of joint where only hyaline is found. It can be temporary or permanent, depending on whether the hyaline tissue is ossified, as at the junction between the epiphysis and the shaft of a bone, or permanent, as occurs between the ribs and the sternum.

2.2. Sinphysis

Symphyses are fibrocartilage or hyaline tissue joints and can be slightly mobile. An example is the pubic symphysis, the junction of the two bones of the pelvis.

3. Synovial joints

The synovial joints are the most functional joints in the body. Its main function is to prevent friction between the bones. They are characterized by:

  • be mobile (diarthrosis);
  • possess a cavity surrounded by a joint capsule and filled with synovial fluid.

Synovial fluid or fluid is produced by the synovium ( synovium ) and the hyaline cartilage covers the entire surface of the bone that is part of the junction.

Synovial joints can be classified according to the movement they allow:

  • hinge,
  • flat or sliding,
  • pivot,
  • condiloide or ellipsoidal,
  • in saddle, and
  • spherical.

Types of joints according to their function

The types of joints according to their function refers to the ability to perform some type of movement between the bones that make it up.

1. Synarthrosis: immobile joints

Synarthrosis are those joints where the bones do not move with each other. Examples we have in the bones that make up the skull.

2. Amphiarthrosis: semi-mobile joints

Semi-mobile joints are classified within the group of cartilaginous joints. Examples of amphiarthrosis we have it between the vertebrae.

3. Diarthrosis: mobile joints

Diarthroses are the joints that allow movement in one or more axes. Structurally they are of the synovial type, and depending on the movement, we find six types.

3.1. Hinge joint

This type of joint is established between the concave side of one bone and the convex side of the other bone. It only allows movement in one axis, such as flexion and extension. Examples of hinge joints are the elbow and the joints between the phalanges.

3.2. Ellipsoidal or condyloid joint

The ellipsoidal or condyloid joint is established between a slight depression of one bone and the rounded portion of other bone (s). It allows movement in two axes:

  • flexion and extension,
  • medial / lateral or abduction / adduction.

The metacarpal-phalangeal joint of the hand is a good example.

3.3. Saddle joint

The saddle joint occurs between bones that have a concave and a convex surface. It can be moved in two axes, allowing flexion / extension and abduction / adduction.

This type of joint is found between the first metacarpus (of the thumb) and the trapezius carpal bone. This allows the thumb to be positioned perpendicular to the hand and the ability of the human thumb to oppose.

3.4. Sliding joint

The sliding or flat joint occurs between bones with flat surfaces of similar size. It could allow movement in various axes, but due to the surrounding ligaments, movement is restricted. Examples are between the bones that form the carpus in the hand and the tarsus in the foot.

3.5. Pivot joint

The pivot joint occurs between two bones with rounded edges within a ring of ligaments. The clearest example is the junction between the first and second vertebrae, which allows the head to move from side to side.

3.6 Ball joint

The spherical or glenoid joint is characterized by having one of the bones with a round head that fits into the concavity of another bone. This joint allows movement in several axes:

  • flexion and extension,
  • abduction and adduction,
  • rotation.

The classic examples of this type of joint are achieved at the junction of the humerus at the shoulder and the head of the femur in the pelvis.

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