Histopathology grading systems for characterisation of human knee osteoarthritis--reproducibility, variability, reliability, correlation, and validity.

OBJECTIVE: To determine the reliability, reproducibility, variability and validity of the Osteoarthritis Cartilage Histopathology (OACH) assessment system and Mankin Histological-Histochemical Grading System (HHGS) when applied to the characterisation of the osteoarthritic human knee.
METHOD: Osteoarthritic knees of 10 patients undergoing unilateral knee arthroplasty were assessed, and assigned Kellgren-Lawrence and Line Drawing Atlas (LDA) radiology scores. The tibial plateaux were scored using the Modified Collins (MC) and Société Française d'Arthroscopie (SFA). Three observers twice scored both the OACH and HHGS across a single complete medial and lateral tibial plateau transect taken to include the region with the most severe osteoarthritis (OA) lesion. Intra- and inter-observer reliability, reproducibility, variability and validity were assessed, and the correlation between the two histopathology scoring systems was calculated. RESULT: Both histopathology scoring systems were determined to be reliable and reproducible exhibiting similar variability, when applied to characterise OA specimens sampled from a well defined patient group with knee OA. A strong correlation between the mean OACH and mean HHGS scores was identified (Spearman's ρ 0.980, P<0.0001).
CONCLUSION: Both scoring systems implemented provide useful measures in the characterisation of knee osteoarthritis. It is of note that an additional parameter within the OACH score over the HHGS defines the extent of the disease, where the HHGS is a grade attributed to the most representative level of the biological aggression within the OA lesions. This study has confirmed the OACH system's utility in human knee OA and is supported by a significant correlation with the established HHGS.