Abstract: Interstitial fluid flow is an important component of themicrocirculation and interstitial environment, yet there is few direct invivo measurement of it within human body. Therefore, computational andmathematical models are employed to investigate the fluid flow especiallywithin cortical bone and ligaments.This article is to investigate the interstitial fluid flow in inter osseousmembrane on lower limb, where the distribution of capillaries is regularparallel arrays on certain direction which is approximate to the directionof parallel collagen fibrils. It' rational to consider the interstitialspace as a porous media and set up a three dimensional filtration model tostudy the flow field. The govern equations of the model is Brinkman equationand conservative equation. A CFD software (FLUENT) is used to executive thenumerical simulation.There are some interesting results. First, interstitial fluid penetratingthrough capillary' walls at artery sections can flow along the direction ofparallel capillaries, and then some interstitial fluid is absorbed bycapillary at vein sections and others outflow at the exit. That is, underparallel capillary distribution condition, there may exit the directionalinterstitial fluid flow. Second, the interstitial fluid flow can beevidently influenced by collagen fibrils. Due to the existence of collagenfibrils in the interstitial space, the velocity distribution of theinterstitial fluid flow tends to be uniform, which is in favor of thephysiological activities of cells. So collagen fibrils are very important tothe organism. Third, pressure is also an important factor to influence theinterstitial fluid flow. The increases of pressure near artery (p_a) andpressure near vein (p_v) can both accelerate the interstitial fluid flow,while increase of pressure in interstitial space (p_i) can decelerate theinterstitial fluid flow. Therefore, changing the pressure in capillaries canadjust the microenvironment which cells live in. Changing the pressure ininterstitial space has more effective effect than pressure changing incapillaries. As we all know, when the tissue is undergone the externalforce, the pressure in the interstitial space will be changed, so theinterstitial fluid flow will also be changed. It may be a potential reasonthat naprapathy has a curative effect on the microcirculation in tissues.