Summary

Proposition a complete assessing of osteoarthritis (OA) joint by a modification of Kellgren and Lawrence scale through a system of scores by individual three knee compartments, and the inter- and intra-observer evaluation

Abstract

Introduction

Kellgren and Lawrence (KL) scale is used to evaluate radiologic imagines of knee OA. In the scientific literature, there is no international consensus on how the best method to evaluate each category of KL should be, and to agree with the radiologist and the orthopedic surgeon on the findings of each category. The option of evaluate an individual three compartment at the same time doesn’t exist. The modification of KL scale is exposed for an individual analysis of knee compartments assigned a score and measures, and given statistical power using a grade of concordances inter and intra-observer, based on radiologic imagines evaluations.

Methods

The modification to the scale was made by informal consensus. Intra-observer and interobserver concordances were evaluated using Krippendorff's alpha coefficient. 210 knee radiographs were evaluated by 6 observers (orthopedic surgeons and radiologists, all with more than 10 years’ experience), in two instances with a 4 weeks interval and assigning them a score.

Results

Based on the KL scale evaluation system was constructed that includes the variables of joint space, osteophytes, subchondral line, spongy subchondral. The individual evaluation of the three compartments of the knee (medial, lateral and patellofemoral) was performed. The result of the interobserver concordance in the first evaluation was 0.48, 0.46 and 0.51, for medial, lateral and patellofemoral compartments, in the second evaluation it was 0.54, 0.56 and 0.61, respectively. An improvement in interobserver concordance was observed in the second evaluation. The intra-observer concordance was moderate to substantial and for some evaluators was almost perfect with concordance ranks between 0.48-0.8, 0.55-0.82 and 0.44-0.83, for medial, lateral and patellofemoral compartments.

Conclusion

The agreement of modified KL scale is moderate to substantial by concordances criteria and we consider that is necessary observe the three compartments at the same time to evaluate OA, and there are not doubts about the utility of KLM scale for the radiological evaluation of knee osteoarthritis.


Key words: osteoarthritis, knee, Kellgren & Lawrence, concordance