Aim of study: Ongoing efforts of the "German Society of Orthopaedic Surgery and Traumatology" (DGOT) to standardize diagnosis and therapy of osteoarthritis, necessitated this study, where the reproducibility of different radiographic features of knee-OA was assessed.
Methods: Three readers graded 100 antero-posterior and lateral knee radiographs for selected features (femorotibial osteophytes, joint space narrowing, sclerosis and chondrocalcinosis; patellofemoral osteophytes) and an overall-score (Kellgren and Lawrence, 1963) at two time points 3 months apart. Intra- and inter-observer-reliability were calculated by intra-class correlation-coefficient (ICC).
Results: Osteophytes in the femorotibial as well as in the patellofemoral joint could be assessed with a high intra- and inter-observer-reliability. While for joint space narrowing intra-observer-reliability is excellent, the inter-observer-reliability is less satisfactory, and subchondral sclerosis as well as chondrocalcinosis showed even less reproducibility. The Kellgren-Lawrence global score proofed to be highly reproducible.
Conclusion: Based on the results of this examination, we can recommend a reliable radiographic classification of knee osteoarthritis by grading of relevant individual features (osteophytes and joint space narrowing) and overall assessment.