symphysis

A symphysis is a type of cartilaginous joint in which two bones are joined by a pad of fibrocartilage. It is considered a secondary cartilaginous joint (amphiarthrosis), allowing limited movement while providing strength and resistance to shear and compression forces.

Structure and characteristics: In a symphysis, the ends of the adjacent bones are covered by a thin layer of hyaline cartilage, and the articular surfaces are united by a thick fibrocartilaginous pad. The joint generally lacks a true synovial cavity and is reinforced by surrounding ligaments. The fibrocartilaginous disc permits small movements and acts as a shock absorber. Nutrient exchange occurs by diffusion due to limited vascularity of the fibrocartilage.

Common examples: The classic example is the pubic symphysis, located at the front of the pelvis where the two pubic bones meet. The intervertebral joints between adjacent vertebral bodies are also described as symphyses, connected by fibrocartilaginous intervertebral discs. In some anatomical references, other midline joints that use fibrocartilage, such as certain sternocostal junctions, are noted as symphyseal types as well.

Function and clinical relevance: Symphyses provide combination strength and flexibility, distributing load and absorbing impact during activities such as walking and lifting. They can permit slight movement to accommodate growth and mechanical demands. Hormonal influences during pregnancy can increase laxity of the pubic symphysis to facilitate childbirth. With age, fibrocartilage may calcify or ossify, reducing mobility. Pathological changes include diastasis after trauma and conditions such as osteitis pubis, which can cause pain and functional limitation.