An arthroscope is an instrument for looking into the knee.
An arthroscope is the main instrument used for keyhole surgery of the knee - ie arthroscopy.
Light is shone into the knee through the arthroscope, which has a small lens at the far end to angle the light beam.
The same instrument has attachments to allow an inflow under pressure of sterile water-based fluid to expand and wash the joint, and an outflow under suction to extract any tissue which has been cut away.
At the other end is an attachment for a camera, which relays the image to a monitor, like a TV.
Both arthroscope and instruments are introduced into the knee via small cuts - called portals.