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Studies have investigated and dismissed the effect of freeze-thaw cycles on both skeletal muscle and on trabecular bone, but have failed to properly address the effects of these storage methods on the integrity of articular cartilage. Preventing cartilage injury is important in minimizing the long term debilitating effects of osteoarthritis. Accurate subfracture injury prediction must take into account the possible effects that freeze thaw cycles may have on the mechanical properties of cartilage tissue. This paper addresses this concern with matched pair testing of various low temperature storage techniques against fresh control groups. Controlled mechanical indention tests were performed on bovine articular cartilage-on-bone specimens to compare stiffness, peak stress, and loading energy of the cartilage. Findings showed that a slow freeze thaw or flash freeze cycle caused cartilage stiffness to decrease by 37% and 31% respectively. Compressive stress at this strain was also lowered by 31% with a single freezing process. These results may be indicative of a weakened extracellular matrix structure caused by the freeze-thaw process. It is still unclear whether these changes in mechanical properties will result in a change in injury susceptibility for articular cartilage.

This paper presents a biotribological study on cartilage wear and friction, using a system of cartilage-on-stainless steel. This study is a part of the ongoing biotribology research by Dr. Furey at the Virginia Polytechnic Institute and State University. Two loads (65 N and 20 N) and three lubricants (saline reference, reference + hyaluronic acid, and bovine synovial fluid) were tested and evaluated using several analysis techniques. These techniques included wear analysis by hydroxyproline measurement, scanning electron microscopy (SEM), histologic sectioning and staining, numerical analysis of friction and specimen displacement data, and Fourier transform infrared (FTIR) analysis. Biochemical wear analysis showed that, under high load, the saline reference generated the most wear, hyaluronic acid produced less wear, and bovine synovial fluid produced the least. Wear was sensitive to load with all three lubricants, but was not significantly affected by the lubricant under low load. SEM photographs and histologic sections showed evidence of plowing and surface delamination, as well as another wear mechanism that produced wear markings perpendicular to the direction of sliding. Opaque films remained on the polished stainless steel disks after saline and hyaluronic acid tests, but not after synovial fluid tests. FTIR analysis of these films, as well as fresh and worn cartilage, showed that the cartilage experienced chemical changes during sliding.