In the embryo, joints develop from the primitive mesenchyme located between the moving components of the maturing skeleton.

The synovium originates from a specialized area known as the interzonal mesenchyme.1 The synovium is not considered to be a true membrane because it lacks the tight intercellular junctions (desmosomes) and associated epithelial structures that separate cells from the vascular network. Instead, the synovium consists of modified connective tissue cells loosely arranged in a bed of hyaluronic acid and collagen. The synovium persists throughout life.