Movement of interstitial water through loaded articular cartilage.

Water transport through articular cartilage and across the articular surface is a major factor controlling the amount and rate of tissue deformation. To study water movement concentration profiles within the tissue were determined using radiotracer techniques. Water movement was spatially and temporally mapped for unloaded, undeformed tissue, after cyclic and dead weight creep, and for recovery following dead weight creep using a uniaxial confined compression configuration to produce one-dimensional fluid movement. In unloaded tissue diffusion rapidly exchanged water by 15 minutes while the gross efflux of fluid during cyclic and dead weight creep compression effectively inhibited any external water influx. During recovery fluid inhibition was restricted when a small surface load was present, and only after complete removal of all surface traction was a large fluid efflux found. The compression and/or collapse of the uppermost surface layer of the tissue is believed responsible for controlling tissue fluid transport and mechanical response.