目的　探讨腘窝囊肿形成的解剖因素。  方法　对30个成人膝关节标本进行解剖：(1)观察半膜肌与腓肠肌内侧头滑液囊(GSB)是否存在，GSB与膝关节滑膜囊的关系；(2)是否存在GSB与膝关节滑膜囊的通道口；(3)向膝关节腔内注射生理盐水，观察当关节腔内压力增大后，关节内液体是否向GSB内外流。  结果　(1)所有标本均存在GSB，40%(12个)标本的GSB与膝关节滑膜腔相通，其余60%(18个)均存在与膝关节滑膜腔相关联的薄弱区；(2)当膝关节腔内压力增大时关节液流向GSB内。  结论　半膜肌与腓肠肌内侧头滑液囊(GSB)是形成腘窝囊肿的解剖基础。

Objective　To explore the possible anatomic factors on forming the popliteal cysts.　Methods　30 adult knee-specimens were dissected and measured.(1)To observe the occurrence of the gastrocnemius semimembranosus bursa (GSB), and explore the relationship of GSB and knee articular cavity; (2) To dissect and observe the channel between GSB and knee articular cavity; (3)To inject physiological saline into joint, and observe whether physiological saline reached to GSB as the result of articular cavity pressure rising.    Results　 (1) GSB was observed in all specimens, and 40% (12 specimens) GSB communicated with knee articular cavity by a channel.(2) Joint fluid appered in GSB following the increased articular cavity pressure.　Conclusions　The gastrocnemius semimembranosus bursa is anatomical basis for forming popliteal cyst.