Influence of Calcified Cartilage Zone Permeability in Mechanical Behavior of Articular Cartilage: A Finite Element Study

Articular cartilage (AC) disease and especially osteoarthrithis (OA) are debilitating conditions that are associated with huge social and economic burdens. To understand the factors involved in initiation and progression of OA, the mechanical state of the cartilage tissue must be first understood [1]. Biphasic and triphasic models developed by Mow and coworkers relate AC structure with its mechanical behavior and provided researchers with valuable models for AC biomechanics [2, 3]. Although much is known about AC and its mechanical properties, the zone of calcified cartilage (ZCC) has been sparsely studied. ZCC is very thin and highly interdigitated with subchondral bone (SB) which makes it very difficult to isolate for independent study [4]. It is well known that SB plays an important role in both initiation and/or progression of OA [5], thus ZCC may also be an important player in the pathology of the disease [6]. A few studies have investigated mechanical properties of ZCC, but conflicting results have been published on ZCC permeability. Although ZCC has been mainly assumed to be impermeable [7], recently Hwang et al. [8] suggested that ZCC may have even higher permeability than cartilage itself. We studied the effect of ZCC permeability on mechanical behavior of AC using a finite element (FE) model.