Reliability of radiographic assessment in osteoarthritis of the knee joint

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-GA 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 interobserver-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.