An assessment of equine cartilage degeneration.

Millions of Americans suffer from osteoarthritis, a joint disease characterized by cartilage degradation and subchondral bone sclerosis. However, little is known about its pathology. It remains to be discovered which comes first in the progression of osteoarthritis: subchondral bone remodeling or cartilage degeneration. This study assessed equine cartilage degeneration, based upon measurements of cartilage thickness and Indian ink stain uptake. By gaining a greater understanding of the determining factors in cartilage degeneration, we may be able to better understand the pathomechanics of osteoarthritis. In seven horses, joint regions of interest were harvested bilaterally and isolated into planar osteochondral samples using a band saw and stored at -20 degrees C. After thawing, the samples' articular surfaces were dyed using an Indian ink stain to highlight articular cartilage degeneration. Digital images of the samples were taken before and after the staining, and mean pixel values for the pre- and post-ink images were measured using image analysis software. Reflectance Score (RS) was calculated using mean pixel values normalized between grayscale calibration standards. Articular cartilage thickness was measured at five random locations on each sample from images taken in the transverse orientation. Statistical analysis found no significant effect of limb side for either RS values or thickness, allowing data from right and left limbs to be grouped for analysis. There is a statistically significant correlation between joint region and thickness, as well as between joint region and RS; however, there was no statistical correlation between thickness and RS.