OARSI osteoarthritis cartilage histopathology assessment system: A biomechanical evaluation in the human knee.

The study compared the OARSI osteoarthritis cartilage histopathology assessment system with the biomechanical quality of human in vivo cartilage samples. In a prospective cohort study, 84 patients (100 knees) with varus deformity of the knee were included between May, 2010 and January, 2012. Osteochondral samples underwent biomechanical and histologic analysis. The dynamic modulus significantly (p < 0.001) decreased with each advancing grade of degeneration from OARSI Grade 0 (surface intact) to OARSI Grade 4 (erosion). For the aggregate modulus, there were significant (p < 0.001) differences between OARSI Grade 0 and OARSI Grade 1 as well as between OARSI Grade 1 and OARSI Grade 2. From OARSI Grade 2 to OARSI Grade 5, no differences in aggregate modulus occurred. The new OARSI grading system provides useful information about the functional properties of cartilage. There is a significant difference in cartilage stiffness between samples with intact surface and no signs of degeneration (OARSI Grade 0) and samples with intact surface and early signs of arthritis (OARSI Grade 1). Surgeons performing joint preserving procedures have to be aware that in knees with an intact cartilage surface (OARSI Grade 0/1), significant differences in the biomechanical properties may exist.