It is to be expected that the extensive researches of Professor Levick and his group on the exchange of water and solutes between synovial fluid and the microcirculation of the synovial lining will advance understanding of the nutrition and lubrication of the synovial joint and of the ways in which disturbances in these processes are involved in joint disease. What is less expected is the way in which this work has raised, and often definitively answered, questions that are pertinent to many other areas of physiology and biophysics.