Aim: The Système Française D’Arthroscopie (SFA) is a validated method of arthroscopic grading and scoring the knee OA. We have validated a modification of the SFA system for use with digital photographs of pathological samples.

Material and Method: After Ethics Committee approval, both tibial plateaux and femoral condyles were collected from 84 patients undergoing total knee replacement or at post mortem. Extent and grading of cartilage changes were documented for the 4 compartments of each sample on a diagram using photographs at standard magnification and illumination, archived, (Photographic Scores). Validation obtained by direct visualisation and probing (Pathological Scores). Radiographic and Histological scoring In addition, each sample was digitally. A second observer (AY) also graded and scored photographic images for 72 compartments of the first 18 cases.

Results: For each of the 4 compartments studied, scores ranged from -2.2 to +717.8, representing the full range of possible scores. A statistically significant correlation observed in the study between radiological variables and the severity of chondropathy assessed by our (SFA-path) [ P < 0.005] suggests satisfactory extrinsic validity of this scoring system. And statistically significant correlation [p> 0.0001] between the SFA Path scores of the medial compartment tibial plateau OA and Histologi-cal grade [Minkin] of the same samples. Allocation of scores to diagrams was highly repeatable (Repeatability Coefficient = 50). There was good agreement between Pathological and Photographic Scores (Repeatability Coefficient = 88). There was moderate agreement between Photographic Scores allocated by the 2 observers, with greatest agreement for low (< 200) and high (> 500) scores. Scores for each compartment correlated with scores for each of the other 3 compartments (R values 0.7 to 0.9, all P < 0.005).

Conclusion: We validated our modified SFA system which permits scoring of OA severity using digital photographs of pathological samples. SFApath is reliable and repeatable scoring system Our data support the view that OA affects the entire joint, and that a single compartment (e.g. medial tibial plateau) can be taken as broadly representative of the tibiofemoral joint as a whole.