The knee has various structures: collateral ligaments, cartilage (joint), meniscus and cruciate ligaments. If there is a knee lesion, more than one of these structures can be injured simultaneously.
The meniscus consists of two half-moon shaped fibro cartilage structures attached to the tibia.  The external meniscus is also known as the lateral meniscus, the internal meniscus as the medial meniscus. Their function is to distribute weight when we walk or run, contributing to knee stability. If they didn’t exist, the joint cartilage would have to support too heavy a load and would be damaged.

Knee arthroscopy is indicated for the treatment of meniscus pathologies, such as joint cartilage lesions, osteochondral lesions, loose bodies within the knee, advanced synovitis, cruciate ligament ruptures and some tibia plateau fractures.

Arthroscopy is an orthopaedic surgery used to view, diagnose and treat problems inside a joint, involving only small incisions. A sterile solution is used to fill the knee joint and all non-transparent fluid is eliminated to provide a clear view. The surgeon introduces the arthroscope to diagnose the problem, using a video image to guide the probe.
After surgery, the surgeon closes up the incisions with either stitches or tape, covering the wound with a plaster.

The doctor will indicate requirements, specific to each patient.

Among the risks related to knee arthroscopy are: post operative bleeding, deep-vein thrombosis, infection, joint rigidity, numbness around the incisions, vessel and nerve lesion as well as compartmental syndrome (compressions of nerves, blood vessels and muscle).
Risks of and complications from arthroscopic surgery of the knee are not significant.

Thigh muscles (quadriceps) and knee tendons need to be strengthened by swimming or riding a bicycle (either fixed or moving).

Depending on results and the surgery itself, three to six weeks is required for full recovery.
After joint cartilage surgery, up to six months will be needed. For anterior cruciate ligament reconstruction, it may be six to nine months before you can return to sports.
Please note that, sometimes, a more serious knee injury has occurred than initially diagnosed and this may affect the recovery period.