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Table 1 Differential diagnosis for cystic lesions in and around the popliteal fossa

From: Lymphangioma of popliteal fossa masquerading as Baker’s cyst

  Ganglion cyst Baker’s cyst Parameniscal cyst Lymphangioma
Age predominance Adults 4–7 years/35–70 years Adults Paediatric
Related structures Joint-related ligament and tendon Gastrocnemius semimenbranosus bursa Meniscocapsular junction Intermuscular plane
Knee joint extension/association ± + +
Ultrasound Well-defined anechoic to hypoechoic lesion with few internal septae Well-defined anechoic cyst extending to the joint space. ‘Speech bubble’ sign
Internal echoes can be seen if infected
Anechoic to hypoechoic cyst with a tear in the adjacent meniscus Multiloculated cystic lesion with thin septations mostly anechoic but can have internal echoes when associated with infection or haemorrhage
MRI T1 hypointense and T2 hyperintense cystic lesion ± few thin internal septations
+/ peripheral post-contrast enhancement
T1 hypointense and T2 hyperintense cystic lesion extending from the joint space
No post-contrast enhancement
T2 hyperintense cyst communicating with a tear in the adjacent meniscus
No post-contrast enhancement
T1 hypointense and T2 hyperintense multiloculated cystic lesion away from the joint
Peripheral and septal enhancement +
Histopathology Thin connective tissue capsule without synovial lining Synovial tissue lining with fibrous component Lined by synoviocytes, collagen and fibroelastic cartilage Macroscopic multiseptated lymphatic spaces