Direct posterior endoscopic excision of atypical popliteal cyst: A case report.

Certain types of popliteal cysts do not possess the common pathophysiology of Baker's cysts, such as location or the presence of a one-way valve lesion. The traditional arthroscopic approach and excision of such atypical popliteal cysts are difficult because they do not communicate with the knee joint, especially when located behind the popliteal neurovascular structure. In this case report, we introduce a direct posterior endoscopic technique for the excision of atypical popliteal cysts when accessing them through the traditional arthroscopic approach is unfeasible. In this case, the popliteal cyst was not located between the gastrocnemius medial head and the semimembranosus muscle and did not communicate with the knee joint. Passage of the popliteal artery was observed running on the anteromedial side of the popliteal cyst. Therefore, a direct posterior endoscopic approach was decided for the surgical treatment of the popliteal cyst, and the atypical popliteal cyst was successfully excised without any complications. We also describe the possible advantages and pitfalls of the direct posterior endoscopic approach. Clinical relevance: Direct posterior endoscopic excision using an intra-cystic portal in the prone position is considered a safe and effective treatment method for atypical popliteal cysts.