Abstract
The compressive stiffness of cartilage is primarlly determined by proteoglycan, whereas the tensile properties are determined by collagen fibres. The first alteration in cartilage structure during cartilage degeneration is the decrease in proteoglycan content and increase in interstitial water; consequently, cartilage becomes softer and cartilage stiffness decreases. The pupose of our study was to evaluate arthroscopically the compressive stiffness of cartilage in different areas of living human knee joints. Detection of softening is revealed in vivo by using an indentation instrument (artscan 200). The instrument is composed of a measurement rod joined to the handle; in the distal end of the rod, there is an inclined flat surface with a separate plane –ended cylindrical indenter. During measurement the distal end of the instrument is pressed against the articular surface while the indenter imposes constant deformation on the cartilage. The maximal indenter force, by which the tissue resists the constant deformation, is measured with strain gauge transducers. We performed indenter tests in knees joints in which cartilage was diagnosed as normal; stiffness of articular cartilage was also measured during arthroscopy in knees before ACL reconstruction, in knees with closed chondromalacia (ICRS grade 0–1) and in osteochondral lesions (ICRS OCD grade 1) and the data compared with areas of normal cartilage.
