On the structural and physiological basis of the influence of exercise, movement and immobilization in inflammatory joint diseases.

In inflammatory joint diseases the protein concentration often is high in the synovial fluid and, in rheumatoid arthritis at least, probably also in the extra-articular connective tissue. This alters the Starling equilibrium. Peculiarities of the circulation of blood and lymph in articular units and basic physiological principles might explain not only why this readily manifests as joint effusions, but also the influence of exercise, movement, immobilization and posture on the activity of non-bacterial synovitides.