A New Method for Determination of the Tensile Modulus of Articular Cartilage In Situ in a Free-Swelling Configuration

Studies of cartilage swelling have been used to demonstrate the effects of collagen network damage associated with osteoarthritis (OA) [1,7]. Elevated swelling, or increased hydration, is generally observed in fibrillated and degenerated cartilage where the integrity of the collagen network is insufficient to restrain the interstitial swelling pressure [8]. We recently developed an experimental method to quantify these swelling effects as components of a swelling-induced strain tensor in free-swelling tests of cartilage in situ [9]. Using this method, we were able to detect changes in swelling strains with cartilage degeneration in the meniscectomy model of OA [10]. In this study, we propose to quantify the material properties of canine and human cartilage studied in the free-swelling test and to compare them with site-matched values measured in uniaxial tensile testing. A triphasic constitutive model [6] was used to predict the components of strain in the free-swelling test for comparison with experimentally measured values. Values for the tensile modulus were found to compare well using the free-swelling and uniaxial testing methods. These findings demonstrate the potential of this new methodology for quantifying cartilage properties in small cartilage samples, such as in small animal models of OA.