Synovial fluid circulation in the hip joint.

Early in our study of the role of incongruency in the hip (Ref. 1) we observed by x-ray screening that, under load, a drop of barium sulphate placed between the articular surfaces spread out between them and a substantial portion was extruded from the intercartilage space into the fossa; all the barium was drawn back as load was reduced. This observation and others (Ref. 2) which demonstrated the location, size and behaviour of intercartilage space with movement and load, prompted exploration of the hypothesis that the space due to joint incongruency serves as a pump to transport synovial fluid in the articular cavity in aid of nutrition and lubrication. This had already been suggested by others (Ref. 3); but none have closely studied the hypothesis. The following is an expansion of this idea, which leads to the concept of a systematic circulation of fluid through the hip joint.