Arthroscopy is a rod-shaped optical instrument with a diameter of about 5mm used to observe the internal structures of joints. It is an endoscope employed for the diagnosis and treatment of joint diseases. The arthroscope has a lens at the end of a thin tube, which is inserted into the joint. The internal structures of the joint are then displayed on a monitor, allowing direct observation. Arthroscopy is not only used for disease diagnosis.

The basic structure of an arthroscope is an optical system. At its center is a rod lens system for image acquisition, surrounded by optical fibers that introduce light, all enclosed in a metal protective sheath. It consists of an arthroscope lens, camera, main unit, monitor, and cold light source. The arthroscope lens is a slender rod over 20 centimeters long and 4-5 millimeters thick, designed for insertion into the joint cavity. The rod contains a set of optical fibers and a lens system; the optical fibers transmit light into the joint, while the lens system transmits images from inside the joint. Externally, a light cable connects the optical fibers to the cold light source, illuminating the joint. A camera connects the lens to the main unit and monitor, displaying the joint's internal images on the screen. By making small incisions of about 0.8mm to 1.0cm in the skin, the arthroscope is inserted into the joint. With a camera and display system attached behind it, the internal morphology and pathologies of the joint can be directly observed. Using specialized instruments, joint diseases can be treated, avoiding the need for many open joint surgeries.