QUANTITATION AND LOCALIZATION OF CARTILAGE DEGENERATION FOLLOWING THEINDUCTION OF OSTEOARTHRITIS IN THE RABBIT KNEE

Objective: To develop and apply a new video imaging technique to quant ify and localize Indian ink staining of cartilage of the rabbit femoro tibial joint after the induction of osteoarthritis by unilateral trans ection of the anterior cruciate ligament (ACLT). Methods: Nine weeks a fter surgery, femora and tibiae from 11 ACLT and contralateral control knees were harvested and positioned to obtain calibrated gray-scale i mages of the ink-painted articular cartilage surfaces that are opposed with the knee in 90 degrees flexion. Images were processed so that ar eas of normal cartilage gave a relatively high reflectance score, wher eas ink-stained fibrillated cartilage and exposed bone gave low scores . Results: Comparison of the medial and lateral femoral condyles and t ibial plateaus (MFC, LFC, MTP, LTP) of control and ACLT knees showed t hat the area of the MTP not covered by the meniscus had a significantl y lower reflectance score (P < 0.001) than other areas. ACLT led to an 11% decrease (P < 0.001) in the overall reflectance score. The reflec tance score decreased as a traditional morphological grading of degene ration increased. ACLT-induced degeneration had a predilection for the posteromedial aspects of the joint, and to a lesser extent, the anter olateral aspects. In the tibial plateaus, ACLT caused significant dege neration in the covered, but not the uncovered, areas. Image scores of opposing cartilage surfaces (i.e., MFC vs MTP and LFC vs LTP) were si gnificantly (R=0.56-0.70, P < 0.001) correlated in ACLT and control kn ees. Discussion: Identification and characterization of cartilage area s prone to degeneration may be particularly useful for further analysi s of biochemical and biomechanical mechanisms in osteoarthritis, as we ll as the efficacy of therapeutic interventions.