Final answer:
The endoscopic instrument used to visualize the interior structures of a joint is called an arthroscope, which is a type of endoscope specifically designed for examining and performing procedures inside joints.
Step-by-step explanation:
The endoscopic instrument used to visualize the interior structures of a joint is called an arthroscope.
An arthroscope is a type of endoscope that is specifically designed for examining and performing procedures inside joints, such as the knee joint. It uses fiber optics to transmit light to illuminate the joint and to transmit images back for observation.