Diagnostic arthroscopy is the keyhole examination of the inside of the knee without actually performing any surgical procedures.
The arthroscope has an integral light source and camera. A second portal allows input of water under pressure, while a third portal allows an instrument such as a probe.
Photographs can be taken through the camera inside the joint. Here is a normal meniscus seated on the tibia bone, with a rounded normal femoral condyle above it.
During a diagnostic arthroscopy a blunt-ended probe is generally used to feel the joint surfaces, examine the menisci and feel for the integrity of the cruciate ligaments.