Figure 4 Arthroscopic visualization of popliteal cysts after methylene blue staining. (A) MRI shows a popliteal cyst located posteriorly within the medial head of the gastrocnemius muscle. (B) Methylene blue staining after drainage of the cystic fluid shows the extent of the cyst wall, which can be clearly identified, thus enabling complete excision of the cyst wall to reduce the recurrence rate of the cyst. (C) Performance after excision of the medial wall of the popliteal cyst.