A Baker's cyst (Baker's cyst or popliteal cyst) is a change consisting in a non-physiological enlargement of the connective tissue space, which is filled with joint fluid. It resembles a lump that can be palpated through the skin when examining the knee. It is located in the popliteal fossa on the posterior side of the thigh between the medial head tendons of the gastrocnemius muscle and the semimembranous muscle.

Symptoms related to the occurrence of the Baker's cyst itself are very rare, but if they do occur, they may be related to its size and advancement, as well as the underlying disease process and inflammation of the knee joint. The most important symptoms that may indicate the presence of a popliteal cyst are:

clearly palpable lumps under the skin at the back of the knee
knee pain worsening with prolonged walking and during physical activity,
redness and warming in the area of ​​the cyst under the knee,
swelling and a feeling of "fullness" in the knee,
limitation of flexion and extension of the knee joint,
depending on the size of the cyst, there may be numbness in the calf area (also when the cyst ruptures), pain and swelling of the lower leg,
limb function limitation.

The arthroscopic procedure consists in removing the cyst, closing its connection with the joint and suturing the damaged joint capsule tightly. In the case of concomitant intra-articular diseases (or causes of secondary occurrence of the cyst), repair activities are also performed. Arthroscopy allows for the least invasive removal of all known and described causes of popliteal cyst formation, which significantly improves the effects of treatment and reduces the number of recurrences. It is performed when conservative treatment does not bring satisfactory results.