[Ultrasound diagnosis of the popliteal fossa]

Sonography of the knee is a well-established method for the diagnosis of palpable tumors. However, evaluation of the menisci, cruciate ligaments, and hyaline cartilage is controversial. Despite the variable echogenicity and extension of different diseases, many distinct sonographic signs are different in cysts, solid neoplasms, and vascular diseases. The investigator must be familiar with various patterns of popliteal cyst formation: crescent-shaped, cross-shaped, slitlike, and grape-like cysts. Because of diagnostic and economic reasons the following concept should provide guidance when diagnosing lesions of the popliteal fossa: the first step of diagnostic imaging should include plain film radiography and sonography. In a second step MRI and/or arthroscopy should be performed.