Fibrous Joints: Definition, Types, Functions and Associated Injuries

The adjacent bones are directly connected to each other by fibrous connective tissue, and therefore the bones do not have a joint cavity between them.

These are fixed joints where the bones are joined by a layer of white fibrous tissue of varying thickness. In the skull, the joints between the bones are called sutures. Such immovable joints are also known as synarthrosis .

Types

Most fibrous joints are also called “fixed” or “immovable” because they do not move.

Sutures

A suture is a type of fibrous joint found only in the skull. The bones are held together by Sharpey’s fibers .

It is normal for many of the skull bones to remain unfused at birth.

Fusion of the skull bones at birth is known as craniosynostosis . The term ‘fontanelle’ is used to describe the resulting ‘weak spots’.

The relative positions of bones continue to change during adult life (although less rapidly), which can provide useful information in forensic medicine and archeology. In old age, the cranial sutures can ossify (become bone) completely.

The joints between the teeth (gomphosis) and the joint between the jaw and the skull, the temporomandibular joint, form the only unsutured joints in the skull.

Types of sutures

Flat sutures: the edges of the bones are aligned with each other as in a normal butt joint.

Silty Sutures – The edges are beveled, so the suture plane is slanted like a miter joint.

Schindylesis:  formed by two bones that are coupled together in a similar way to a bridle joint.

Serrated Sutures – Similar to a denticulated suture, but the interlocking regions are serrated rather than square.

Suture list
Visible from the side
  • Coronal suture: between the frontal and parietal bones.
  • Sutura lambdoidea.
  • Ssutura occipitomastoidea.
  • Occipitomastoid suture: between the occipital and temporal bones and continues with the lambdoid suture.
  • Sphenofrontal suture.
  • Sphenoparietal suture.
  • Sphenoeschymal suture.
  • Sphenozygomatic suture.
  • Squamosal suture: between the parietal and the temporal bone.
  • Zygomaticotemporal suture.
  • Zygomatofrontal suture.
Visible from the front
  • Frontal suture : between the two frontal bones, before the fusion of the two into a single bone.
  • Sagittal suture : along the midline, between the parietal bones.
Visible from below or within
  • Frontoethmoidal suture.
  • Petrosquamous suture.
  • Sphenoethmoidal suture.
  • Sphenopetrosal suture.

Sindesmosis

A syndesmosis is a slightly mobile fibrous joint in which bones such as the tibia and fibula are joined by connective tissue.

Examples include the distal tibial joint of the tibia, as well as the radioulnar joint. Syndesmosis injuries of the ankle are commonly known as a “high ankle sprain.”

Although syndesmosis is a joint, in the literature the term syndesmotic injury is used to describe injury to the syndesmotic ligaments.

Diagnosis of a syndesmotic injury

Diagnosis of syndesmosis lesions by physical examination is usually straightforward. Physical examination findings that are often positive include compression testing and external rotation testing.

Patients with high-grade syndesmosis injuries are often unable to perform a single-leg heel augmentation. Patients report pain over the anterior and often posterior joint of the distal peroneal joint.

Gomfosis

A gomphosis, also known as a dentoalveolar syndesmosis, is a joint that joins the teeth to the bony tooth sockets in the jawbone and jawbone.

The fibrous connection between a tooth and its socket is a periodontal ligament. Specifically, the connection is made between the maxilla or mandible towards the cementum of the tooth.

The movement of a gomphosis is minimal, although considerable movement can be achieved over time, the basis of the use of braces to realign the teeth. The joint can be considered a synarthrosis.

Gomphosis is the only type of joint in which a bone does not join another bone, as the teeth are not technically bony. In the modern, more anatomical classification of the joint, the gomphosis is simply considered a fibrous joint because the tissue that joins the structures is ligamentous.

A gomphosis is a specialized fibrous joint in which a conical process or pin from one bone fits into a hole or socket in another bone. A small amount of fibrous tissue holds the bones together. No movement is possible at such pin and socket joints.