The structure of joints are bones articulating together allowing mobility to the human body. The articulating surfaces of the bones are covered by smooth surfaces that are the cartilage, to allow frictionless bone work together.
In order to protect and cover this cartilage, the joints have a membrane that covers them called the synovial membrane that produces synovial fluid and lubricates and nourishes the joint.
To keep the joints healthy, it is advisable to prevent being overweight and to do physical activity at least three times a week, with less intense exercises preferred (for joints) and to maintain good posture (straight) throughout the working day.
If you have joint pain or inflammation in a joint; rest is advisable due to the overuse of an inflamed joint that can cause irreversible damage.