Lindgren P G
Acta Radiol Diagn (Stockh). 1978;19(2):377-88. doi: 10.1177/028418517801900213.
Pressure measurements in the knee joint and gastrocnemio-semimembranosus bursa were performed on patients and autopsy cases. A normally occurring closure mechanism between the joint and the bursa was demonstrated and analysed. Two patients were also found to have a partial valvular mechanism in the form of a hindrance to spontaneous passage of fluid from the bursa to the joint but no hindrance in the other direction.