Aphiarthrosis: Anatomy, Definition, Function, Primary and Secondary

In anatomy, “articulation” refers to a structural arrangement that holds two or more contiguous bone surfaces together.

Therefore, the joint represents a set of elements (fibrous tissue and cartilage, ligaments, capsules, and membranes) that regulate the connection between two bony segments.

An articulation is a point in the body where the bones meet. They make movement possible by making the skeleton flexible.

The prominent bones that form the joints include the following:

  • Synovial joints: joints of the knee, wrist, shoulder, elbow, ankle, and hip (can move freely).
  • Semi-mobile unions: articulation of the spine (restricted flexibility or amphiarthrosis).
  • Fixed joints: joints of the bones of the skull or pelvis (immovable).

Joints are classified by how much movement they allow (function) or what they are made of (structure). Most allow free movement, some only allow movement in specific ways (amphiarthrosis), and others do not allow movement.

We speak respectively of synovial joints, synarthrosis, and amphiarthrosis joints through scientific terminology.

When it comes to joint disorders, the three most common types include osteoarthritis, arthritis, and traumatic injuries. Osteoarthritis is a common joint disorder and occurs when the joints swell and are more difficult to move.


Arthritis is a joint condition that causes inflammation of one or more joints. Traumatic injuries are characterized by two bones that separate from their meeting point.

They can be caused by a fall, a sudden impact, or another form of trauma. Other disorders include cancers and congenital disabilities (such as hip dislocation).

Seeking medical attention is essential to verify the cause of the disorder and determine the most appropriate form of treatment. Most treatment options tend to depend mainly on the disorder in question, its severity, and the condition of an individual.

They may include treatment with antibiotics and physiotherapy; however, in more severe cases, surgery may be necessary.

What is amphiarthrosis? Definition

The joints of amphiarthrosis, also known as semi-mobile joints, refer to joints characterized by limited movement. Such examples include the vertebra, the ribs, and the spine.

In the articulation of the spine, the bones that form the joints are covered with cartilage and joined by interosseous and peripheral ligaments that only allow the execution of some movements.

The slightly mobile joints are part of the skeletal system and include the joints between the vertebrae and the symphysis pubis.

There are two types of amphiarthrosis joints:

  • Symphysis: a slightly mobile joint in which the joint surfaces of the articulated bones are covered with hyaline cartilage, and the bones are joined by a fibrocartilage layer. For example, the pubic symphysis and the sacrococcygeal symphysis.
  • Sinchondrosis: an immovable joint in which the material connects the joint surfaces is the hyaline cartilage—for example, the first sternocostal joint.

 What function do the joints of amphiarthrosis serve?

The primary function of the joints is to allow both movement and flexibility. They tend to be classified by the degree of their possible movement, the number of bones involved, and the complexity of the joint.

The primary function of the joints of amphiarthrosis is to allow specific movements of the body, as well as to act as support structures.

What are the primary cartilaginous joints?

These cartilaginous joints are composed entirely of hyaline cartilage and are known as syndromes. Most exist between ossification centers of developing bones and are absent in the mature skeleton, but some persist in adults.


  • Sinchondrosis of the pelvis, for example, is ischiopubic synchondrosis.
  • Sinchondrosis of the base of the skull, for example, petro-occipital synchondrosis.
  • The first sternocostal joint is between the first rib and the handlebar (all other sternocostal joints are flat synovial joints).

What are the secondary cartilaginous joints?

These are permanent joints that are composed of fibrocartilage. They are considered amphiarthrosis, meaning they only allow a slight movement and are in the midline of the skeleton.


  • Symphysis pubis between the right and left pubic bones.
  • Manubriosternal articulation between the sternal body and the manubrium.
  • Intervertebral discs.
  • Sínfisis sacrococcígea.
  • Spine.

The spine joints, like other typical joints, involve joining two or more bones.

However, those in the spine involve the vertebral bodies and between the vertebrae and surrounding bones and cartilage, for example, the costovertebral joints.

The joints of the spine, therefore, include:

  • Joints of the vertebral bodies.
  • Joints of the vertebral arches.
  • Craniovertebral joints (atlantoaxial and atlanto-occipital joints).
  • Costovertebral joints.
  • Sacroiliac joints.

Also typical of most somatic joints are the ligaments that serve to strengthen and stabilize such joints.

The ligaments found in the joints of the spine function to support/maintain articulated bones and structures that form the vertebral joints and resist hyperflexion and hyperextension of the spine.