Synovial fluid is the joint's lubricant; gentle movement is a working picture of helping it circulate.
In 📝Articular Mobility this is anatomy language, not a claim the practitioner produces, drains, or medically alters the fluid. Moving through the range the joint already has is how the joint is given a chance to feel less dry or sticky. It is not a diagnosis of too little fluid.
Clients may feel less sticky after easy movement. That feeling is not a lab result.