Popliteal cyst on magnetic resonance (MR) arthrogram

A 54-year-old woman presents with pain and a prior history of meniscal surgery. Image A is a cross-table lateral examination of the knee following injection of contrast into the joint under fluoroscopic guidance, and it shows a popliteal cyst (arrow). Image B is a sagittal projection using a fat-saturated T1 sequence, and shows the contrast-filled popliteal cyst (arrow). Image C is an axial projection using fat-saturated T1 sequence, and shows the popliteal cyst (arrow) communicating with the knee joint (arrowhead).