[Magnetic resonance imaging (MRI) of the bursa around the knee joint]

Since fluid filled bursae lead to visible structures on MR images it is important to establish criteria to recognize them and to differentiate them from tumorous fluid-like structures. With this study the bursae around the knee joint were analyzed for potential differential diagnostic criteria such as localisation, size and shape.

In a retrospective study of 133 MR exams the frequency, localization and morphology were registered. The frequency of occurrence was correlated with the frequency of an effusion by means of the chi 2 test.

The most frequently recognized bursae were bursa subtendinea musculi gastrocnemii medialis (54.9%), bursa musculi semimembranosi (21%), and bursa infrapatellaris profunda (18.8%). 8 different bursae were identified in complete. Size roanged from 2 to 18 mm. The shape was round and ovoid. The bursa subtendinea musculi gastrocnemii medialis and bursa musculi semimembranosi correlated with the occureance of an effusion.

Bursae around the knee are frequently visualized as asymptomatic fluid like structures. Knowledge of the typical localization, size and contour is important for identification and differentiation diagnosis against ganglia, cysts or joint recesses.