Arthroscopy is a well established procedure, which for many patients results in a long-lasting fundamental improvement of joint function. Through minimally invasive incisions into the joint cavity the surgical instruments are inserted, as well as a light source, an imaging device, and in-and-out portals for the rinsing fluid.
During the arthroscopic procedure the joint is flushed with a rinsing solution - usually a saline - in order to wash out the cloudy joint liquid. This allows the surgeon to have a clear view for the surgical operation, and it rinses away any deposits or residue present in the joint cavity.
Here you can see an illustration of what happens inside the joint cavity during the arthroscopic procedure:
After the surgical operation, the rinsing solution will be drained away. The joint space is now "dry", because the viscous synovial fluid was rinsed out, and it will take some time before the body has produced new synovial fluid. During this time the cartilage metabolism is compromised and the cartilage surfaces have no protective layer.