The presence of a cyst in the joint is relatively frequent. These may be composed of fatty or lipomatous material, mucoid material, chondral tissue or synovial tissue. Its location is highly variable and can even be within the cruciate ligaments. Sometimes these entities occur without being as well defined as a cyst, like in cruciate ligament mucoid degeneration. They are conditions that cause pain that is difficult for the patient to define. It is often located in the posterior region of the knee and increases at full extension or upon squatting. In some cases, they may be associated recurrent effusions and joint locks. Arthroscopic resection has a very high success rate. However, it must be performed by expert hands. Otherwise, ligamentous structures essential to the normal functioning of the knee may be inadvertently injured.