Objective: Severity of structural change in knee osteoarthritis (OA) can be measured radiologically, macroscopically or microscopically. Existing methods have limitations for use in laboratory studies. We have developed a Photographic Chondropathy Score (PCS) for use with pathological samples. We have compared the ability of the different severity measures to distinguish between samples obtained at total knee replacement surgery or postmortem (PM), and to detect associations between structural severity and synovitis.
Method: Tibial plateaux and femoral condyles were collected from 84 patients undergoing surgery or PM. Each sample was photographed and scored. Limits of agreement and repeatability coefficients were calculated for PCS. Scores for radiological joint space narrowing (JSN) and osteophytes, histological cartilage changes (Mankin), and synovitis were assigned. Data were analysed using Mann-Whitney U tests, Spearman's correlation coefficient or logistic regression.
Results: A total of 116 knees were analysed from 84 patients. Both medial tibial plateaux and total joint PCS showed good repeatability, internal consistency and reliability between observers. PCS, radiographic and Mankin's scores were all modestly positively correlated (r values 0.28-0.55). PCS and Mankin scores were greater in surgical than PM samples. Synovial inflammation was associated with higher PCS and radiological JSN scores (r values 0.43-0.48), irrespective of diagnosis.
Conclusion: Macroscopic, microscopic and radiographical severity scores are complementary measures of structural severity in knee OA. Synovial inflammation was associated with increased OA structural severity, suggesting a possible role of chronic synovitis in cartilage damage.