A 50-year old female patient with unilateral knee pain demonstrated a recurrent ultrasound-proven popliteal cyst (Baker's cyst). Even though a proper differential diagnosis was done, the MRT of the knee showed in a secondary step a tibial fissure as the cause of the treatment-refractory knee pain and Baker's cyst. A fracture of the tibia is a rare cause for a symptomatic Baker's cysts. Mechanical, degenerative or inflamed diseases of the joint are more frequent associated with a Baker's cyst.