MRI of the bursa around the knee.

Since fluid filled bursae lead to visible structures on MR images it is imp ortant to establish criteria to recognize them and to differentiate them fr om tumorous fluid-like structures. With this study the bursae around the kn ee joint were analyzed for potential differential diagnostic criteria such as localisation, size and shape. Material and methods: In a retrospective s tudy of 133 MR exams the frequency, localization and morphology were regist ered. The frequency of occurrence was correlated with the frequency of an e ffusion by means of the chi(2) test. Results: The most frequently recognize d bursae were bursa subtendinea musculi gastrocnernii medialis (54.9%), bur sa 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 gastrocne mii medialis and bursa musculi semimembranosi correlated with the occureanc e of an effusion. Conclusion: Bursae around the knee are frequently visuali zed as asymptomatic fluid like structures. Knowledge of the typical localiz ation, size and contour is important for identification and differentiation diagnosis against ganglia, cysts or joint recesses.