Joint is innervated by the articular brances of the nerves which supply the muscles which move the joint (Hilton’s law). The fibrous capsule is the most sensitive part of a joint.
Pattern of nerve supply to the capsule of the joint:
The area of the capsule stretched during the action of a muscle is supplied by the articular branch of the nerve which supplies its antagonist. For example, the part of the capsule of the hip joint which is stretched during abduction of hip is innervated by the obturator nerve which supplies the adductors of hip. This acts as a safety mechanism which helps to prevent injury to the joint.