Tensile properties of human knee joint cartilage: I. Influence of ionic conditions, weight bearing, and fibrillation on the tensile modulus

TLDR

The intrinsic tensile modulus of the extracellular matrix of human knee joint cartilage was measured in an isometric tensile apparatus at equilibrium for normal, fibrillated, and osteoarthritic tissues across high‑ and low‑weight‑bearing areas and multiple depth zones. The cartilage exhibited linear stress‑strain behavior up to ~15 % strain, with intrinsic tensile moduli below 30 MPa that were higher in low‑weight‑bearing regions and correlated with collagen/proteoglycan ratio, while osteoarthritic tissue showed stiffness below 2 MPa.

Abstract

Abstract The flow‐independent (intrinsic) tensile modulus of the extracellular matrix of human knee joint cartilage has been measured for normal, fibrillated, and osteoarthritic (removed from total knee joint replacements) cartilage. The modulus was determined in our isometric tensile apparatus and measured at equilibrium. We found a linear equilibrium stress‐strain behavior up to ∼15% strain. The modulus was measured for tissues from the high and low weight‐bearing areas of the joint surfaces, the medial femoral condyle and lateral patello femoral groove, and from different zones (surface, subsurface, middle, and middle‐deep) within the tissue. For all specimens, the intrinsic tensile modulus was always less than 30 MPa. Tissues from low weight‐bearing areas (LWA) are stiffer than those from high weight‐bearing areas (HWA). The tensile modulus of the ECM correlates strongly with the collagen/proteoglycan ratio; it is higher for LWA than for HWA. Osteoarthritic cartilage from total knee replacement procedures has a tensile stiffness less than 2 MPa.