Table 2.

Inter-rater reliabilty of knee osteoarthritis scoring systems

Scoring System	Gwet’s AC1 (95% confidence interval)*
IKDC grade	0.71 (0.65–0.77)
Modified Kellgren Lawrence (KL) grade	0.48 (0.41–0.55)
OARSI grade (all criteria)	0.84 (0.82–0.86)
Medial joint space narrowing	0.78 (0.72–0.83)
Lateral joint space narrowing	0.91 (0.88–0.95)
Medial femoral osteophyte	0.94 (0.91–0.97)
Lateral femoral osteophyte	0.77 (0.73–0.84)
Medial tibial osteophyte	0.77 (0.72–0.83)
Lateral tibial osteophyte	0.84 (0.79–0.88)

^*Landis and Koch²⁰ suggest the following benchmark scale for interpreting inter-rater agreement: <0.00 poor; 0.00–0.20 slight; 0.21–0.40 fair; 0.41–0.60 moderate; 0.61–0.80 substantial; 0.81–1.00 almost perfect.