symfysis

A symphysis is a type of cartilaginous joint in which two bones are united by a pad of fibrocartilage and are covered by a thin layer of hyaline cartilage at the articulating surfaces. It is classified as a secondary cartilaginous joint, meaning it allows limited movement compared with a synovial joint, and it functions primarily as a resilient, weight-bearing articulation that can absorb compressive forces.

Structure and development: In a symphysis, the bones meet at a fibrocartilaginous interposed disc or pad that provides both toughness and some elasticity. The joint surfaces are typically connected by a fibrous capsule and reinforced by ligaments. Surrounding hyaline cartilage may coat the contacting surfaces, and the fibrocartilaginous disc reduces friction while distributing loads. These joints often develop from mesenchymal tissue during fetal life and remain connected by fibrous tissue that may ossify or ossify partially with age.

Examples: Classic examples of symphyses include the pubic symphysis between the two pubic bones, the mandibular symphysis between the two halves of the mandible, and intervertebral joints where adjacent vertebral bodies are joined by intervertebral discs. The manubriosternal joint is another example, formed by a fibrocartilaginous connection between the sternum’s manubrium and body.

Function and clinical relevance: Symphyses provide stability while permitting a small amount of movement to absorb shocks from locomotion and loading. They play a crucial role in childbirth, as the pubic symphysis becomes more lax under hormonal influence to allow pelvic expansion. Pathological changes can include pain from malalignment, degenerative disc disease affecting adjacent joints, or diastasis of the pubic symphysis in pregnancy or trauma.