R. Mund ( Leipzig ) / U. Wachter ( Halle )  

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12 Years  

Female  

Leg-Other and unknown  

other  

12 year-old girl with asymptomatic, tightly elastic swelling in the left medial popliteal fossa. On the right side, the knee was clinically and upon palpation unnoticeable.  

A Baker cyst is a synovial outpouching in the sense of a popliteal herniation, whose matrix is the bursa of the semimembranosus muscle underneath the medial head of the gastrocnemius muscle and the joint capsule. It is filled with clear to yellowish fluid. The peak age in childhood lies within the first decade of life; in adults, the incidence increases with age. Male patients are afflicted more often 2:1. Sonographically, one sees mostly cysts without echoes which are limited by a capsule. In echogenic (fibrin) and/or septated contents, one must differentiate between a Baker cyst and other rheumatic illnesses. Treatment consists of surgical resection in toto. In rare cases, an arthroscopy may be necessary to close the cyst with fibrin. There is a chance of reoccurrence.  

<- view Ultrasound 1

Ultrasound 1: Right knee joint, dorsally: This image shows a fluid-filled cyst which is dorsal to the joint space. It shows the connection between the joint space and the cyst ( = Baker's cyst in the original sense)




<- view Ultrasound 2

Ultrasound 2: Longitudinal: right knee joint.

 

Imaging including endoscopy  

Popliteal aneurysm (surely differentiated by color-doppler)  

The resection must be done in toto, otherwise there is danger of reoccurrance.

In asymptomatic, functionally and cosmetically non-impairing cysts, a control-examination of the findings and waiting is recommended, since a spontaneous regression in childhood is described (up to 75%!).  

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Baker cyst, Knee, Popliteal fossa, Popliteal cyst, Baker cyst of the knee joint, child, childhood, pediatric radiology  

R Mund. Baker cysts of the knee joints on both sides. PedRad [serial online] vol 2, no. 7.
URL: www.PedRad.info/?search=20020702144145