This study numerically investigates the pathological changes of fluid flow in cartilage contact gap due to the changes in cartilage surface roughness and synovial fluid characteristics in osteoarthritic (OA) condition. First, cartilage surface topographies in both healthy and OA conditions are constructed using a numerical approach with consideration of both vertical and horizontal roughness. Then, constitutive equations for synovial fluid viscosity are obtained through calibration against previous experimental data. Finally, the roughness and synovial fluid information are input into the gap flow model to predict the gap permeability. The results show that the rougher surface of OA cartilage tends to decrease gap permeability by around 30%–60%. More importantly, with the reduction in gap size, the decrease in gap permeability becomes more significant, which could result in an early fluid ultrafiltration into the tissue. Moreover, it is demonstrated that the pathological synovial fluid has more deleterious effects on the gap permeability than the OA cartilage surface, as it could potentially increase the gap permeability by a few hundred times for pressure gradients less than 10⁶ Pa/m, which could inhibit the fluid ultrafiltration into the tissue. The outcomes from this research indicate that the change in fluid flow behaviour in contact gap in OA condition could significantly affect the function of articular joints.

这项研究数值研究由于骨关节炎（OA）情况下软骨表面粗糙度和滑液特性的变化而引起的软骨接触间隙中流体流动的病理变化。首先，在健康和OA条件下，使用数值方法构造垂直和水平粗糙度的软骨表面形貌。然后，通过根据先前的实验数据进行校准，获得滑液粘度的本构方程。最后，将粗糙度和滑液信息输入到间隙流动模型中以预测间隙渗透率。结果表明，OA软骨的粗糙表面倾向于使间隙渗透性降低约30％–60％。更重要的是，随着间隙尺寸的减小，间隙渗透性的降低变得更加明显，这可能导致早期液体超滤进入组织。此外，已证明病理性滑液对间隙渗透性的影响比OA软骨表面更有害，因为对于压力梯度小于10的关节液，它可能潜在地将间隙渗透性提高数百倍。⁶  Pa / m，可抑制液体超滤进入组织。这项研究的结果表明，OA条件下接触间隙中流体流动行为的变化可能会显着影响关节的功能。