Interreader and intrareader reliability for categorical variables. Weighted κ (95% CI; percent agreement).
| Variable | Comparison | Reader 1 | Reader 2 | Reader 3 | |||
|---|---|---|---|---|---|---|---|
| Left Knee | Right Knee | Left Knee | Right Knee | Left Knee | Right Knee | ||
| KL score | Gold standard | 0.71 (0.52, 0.9; 73%) | 0.56 (0.39, 0.73; 55%) | 0.85 (0.72, 0.97; 85%) | 0.70 (0.56, 0.85; 73%) | 0.81 (0.68, 0.95; 82%) | 0.63 (0.49, 0.77; 64%) |
| Reader 1 | 0.72 (0.54, 0.89; 79%) | 0.74 (0.58, 0.9; 76%) | 0.78 (0.63, 0.94; 82%) | 0.77 (0.62, 0.92; 76%) | 0.75 (0.58, 0.93; 82%) | 0.66 (0.49, 0.83; 67%) | |
| Reader 2 | 0.78 (0.63, 0.94; 82%) | 0.77 (0.62, 0.92; 76%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | 0.97 (0.91, 1; 97%) | 0.83 (0.69, 0.97; 85%) | |
| Reader 3 | 0.75 (0.58, 0.93; 82%) | 0.66 (0.49, 0.83; 67%) | 0.97 (0.91, 1; 97%) | 0.83 (0.69, 0.97; 85%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | |
| Alignment (varus or valgus) | Reader 1 | 0.94 (0.82, 1; 97%) | 0.93 (0.8, 1; 97%) | 0.76 (0.54, 0.97; 88%) | 0.93 (0.8, 1; 97%) | 0.88 (0.72, 1; 94%) | 0.8 (0.59, 1; 91%) |
| Reader 2 | 0.76 (0.54, 0.97; 88%) | 0.93 (0.8, 1; 97%) | 1 (1, 1; 100%) | 0.87 (0.64, 1; 93%) | 0.87 (0.71, 1; 94%) | 0.87 (0.7, 1; 64%) | |
| Reader 3 | 0.88 (0.72, 1; 94%) | 0.8 (0.59, 1; 91%) | 0.87 (0.71, 1; 94%) | 0.87 (0.7, 1; 64%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | |
| Lateral femoral osteophyte | Gold standard | 0.5 (0.3, 0.7; 52%) | 0.45 (0.26, 0.63; 52%) | 0.49 (0.27, 0.71; 49%) | 0.43 (0.2, 0.65; 55%) | 0.53 (0.34, 0.73; 55%) | 0.39 (0.19, 0.58; 55%) |
| Reader 1 | 0.58 (0.4, 0.76; 58%) | 0.63 (0.43, 0.82; 70%) | 0.59 (0.38, 0.81; 67%) | 0.62 (0.42, 0.82; 67%) | 0.61 (0.41, 0.8; 67%) | 0.45 (0.24, 0.66; 55%) | |
| Reader 2 | 0.59 (0.38, 0.81; 67%) | 0.62 (0.42, 0.82; 67%) | 0.4 (−0.02, 0.82; 69%) | 0.42 (0.12, 0.71; 53%) | 0.72 (0.56, 0.88; 73%) | 0.64 (0.46, 0.82; 67%) | |
| Reader 3 | 0.61 (0.41, 0.8; 67%) | 0.45 (0.24, 0.66; 55%) | 0.72 (0.56, 0.88; 73%) | 0.64 (0.46, 0.82; 67%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | |
| Lateral joint space narrowing | Gold standard | 0.57 (0.35, 0.8; 61%) | 0.65 (0.43, 0.88; 70%) | 0.71 (0.51, 0.91; 76%) | 0.63 (0.41, 0.85; 64%) | 0.71 (0.53, 0.89; 73%) | 0.75 (0.6, 0.91; 73%) |
| Reader 1 | 0.76 (0.57, 0.96; 82%) | 0.69 (0.46, 0.93; 76%) | 0.79 (0.61, 0.97; 82%) | 0.65 (0.4, 0.9; 76%) | 0.86 (0.72, 1; 88%) | 0.73 (0.52, 0.93; 79%) | |
| Reader 2 | 0.79 (0.61, 0.97; 82%) | 0.65 (0.4, 0.9; 76%) | 0.81 (0.58, 1; 88%) | 0.68 (0.37, 0.99; 73%) | 0.93 (0.84, 1; 93%) | 0.81 (0.62, 0.99; 85%) | |
| Reader 3 | 0.86 (0.72, 1; 88%) | 0.73 (0.52, 0.93; 79%) | 0.93 (0.84, 1; 93%) | 0.81 (0.62, 0.99; 85%) | 0.92 (0.76, 1; 94%) | 0.92 (0.75, 1; 93%) | |
| Lateral tibial osteophyte | Gold standard | 0.46 (0.24, 0.68; 55%) | 0.57 (0.38, 0.76; 64%) | 0.53 (0.34, 0.72; 58%) | 0.62 (0.45, 0.79; 64%) | 0.46 (0.27, 0.66; 52%) | 0.67 (0.49, 0.85; 70%) |
| Reader 1 | 0.64 (0.47, 0.82; 67%) | 0.65 (0.49, 0.81; 70%) | 0.81 (0.65, 0.97; 85%) | 0.63 (0.47, 0.79; 70%) | 0.73 (0.54, 0.92; 79%) | 0.61 (0.46, 0.77; 67%) | |
| Reader 2 | 0.81 (0.65, 0.97; 85%) | 0.63 (0.47, 0.79; 70%) | 0.45 (0.13, 0.78; 69%) | 0.73 (0.48, 0.98; 80%) | 0.92 (0.8, 1; 94%) | 0.74 (0.58, 0.9; 79%) | |
| Reader 3 | 0.73 (0.54, 0.92; 79%) | 0.61 (0.46, 0.77; 67%) | 0.92 (0.8, 1; 94%) | 0.74 (0.58, 0.9; 79%) | 0.87 (0.65, 1; 94%) | 0.9 (0.72, 1; 93%) | |
| Medial femoral osteophyte | Gold standard | 0.73 (0.56, 0.9; 73%) | 0.53 (0.33, 0.73; 58%) | 0.61 (0.45, 0.77; 61%) | 0.54 (0.33, 0.74; 61%) | 0.61 (0.41, 0.81; 67%) | 0.44 (0.22, 0.65; 55%) |
| Reader 1 | 0.56 (0.37, 0.74; 61%) | 0.52 (0.31, 0.74; 64%) | 0.65 (0.5, 0.81; 64%) | 0.73 (0.56, 0.89; 76%) | 0.55 (0.38, 0.71; 52%) | 0.75 (0.56, 0.94; 82%) | |
| Reader 2 | 0.65 (0.5, 0.81; 64%) | 0.73 (0.56, 0.89; 76%) | 1 (1, 1; 100%) | 0.78 (0.48, 1; 93%) | 0.87 (0.75, 0.99; 88%) | 0.68 (0.49, 0.87; 73%) | |
| Reader 3 | 0.55 (0.38, 0.71; 52%) | 0.75 (0.56, 0.94; 82%) | 0.87 (0.75, 0.99; 88%) | 0.68 (0.49, 0.87; 73%) | 0.81 (0.58, 1; 88%) | 0.91 (0.76, 1; 93%) | |
| Medial joint space narrowing | Gold standard | 0.55 (0.41, 0.7; 52%) | 0.67 (0.51, 0.82; 56%) | 0.73 (0.58, 0.89; 76%) | 0.71 (0.53, 0.9; 73%) | 0.64 (0.5, 0.79; 67%) | 0.76 (0.62, 0.9; 73%) |
| Reader 1 | 0.79 (0.67, 0.91; 76%) | 0.80 (0.68, 0.93; 76%) | 0.74 (0.62, 0.85; 70%) | 0.67 (0.49, 0.86; 67%) | 0.76 (0.62, 0.91; 76%) | 0.73 (0.59, 0.87; 67%) | |
| Reader 2 | 0.74 (0.62, 0.85; 70%) | 0.67 (0.49, 0.86; 67%) | 0.9 (0.77, 1; 94%) | 1 (1, 1; 100%) | 0.91 (0.82, 1; 91%) | 0.84 (0.67, 1; 88%) | |
| Reader 3 | 0.76 (0.62, 0.91; 76%) | 0.73 (0.59, 0.87; 67%) | 0.91 (0.82, 1; 91%) | 0.84 (0.67, 1; 88%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | |
| Medial tibial osteophyte | Gold standard | 0.64 (0.48, 0.8; 61%) | 0.49 (0.23, 0.75; 67%) | 0.75 (0.6, 0.9; 73%) | 0.45 (0.19, 0.72; 64%) | 0.75 (0.6, 0.89; 73%) | 0.48 (0.21, 0.75; 67%) |
| Reader 1 | 0.63 (0.44, 0.81; 64%) | 0.67 (0.47, 0.88; 76%) | 0.7 (0.53, 0.87; 70%) | 0.79 (0.61, 0.96; 85%) | 0.64 (0.46, 0.82; 64%) | 0.82 (0.66, 0.99; 88%) | |
| Reader 2 | 0.7 (0.53, 0.87; 70%) | 0.79 (0.61, 0.96; 85%) | 0.78 (0.54, 1; 81%) | 0.83 (0.61, 1; 87%) | 0.94 (0.85, 1; 94%) | 0.87 (0.72, 1; 91%) | |
| Reader 3 | 0.64 (0.46, 0.82; 64%) | 0.82 (0.66, 0.99; 88%) | 0.94 (0.85, 1; 94%) | 0.87 (0.72, 1; 91%) | 1 (1, 1; 100%) | 1 (1, 1; 100%) | |
| Patellofemoral joint space narrowing | Gold standard | 0.25 (−0.12, 0.62; 46%) | 0.7 (0.44, 0.95; 71%) | 0.33 (0.08, 0.58; 54%) | 0.79 (0.59, 0.99; 81%) | 0.3 (0.08, 0.51; 46%) | 0.79 (0.55, 1; 85%) |
| Reader 1 | 0.69 (0.5, 0.89; 77%) | 0.78 (0.59, 0.97; 77%) | 0.55 (0.31, 0.78; 69%) | 0.74 (0.51, 0.97; 77%) | 0.32 (0.07, 0.57; 54%) | 0.69 (0.38, 0.99; 76%) | |
| Reader 2 | 0.55 (0.31, 0.78; 69%) | 0.74 (0.51, 0.97; 77%) | 0.66 (0.31, 1; 85%) | 0.74 (0.35, 1; 78%) | 0.81 (0.62, 1; 85%) | 0.83 (0.64, 1; 86%) | |
| Reader 3 | 0.32 (0.07, 0.57; 54%) | 0.69 (0.38, 0.99; 76%) | 0.81 (0.62, 1; 85%) | 0.83 (0.64, 1; 86%) | 0.78 (0.63, 0.94; 85%) | 0.79 (0.49, 1; 78%) | |
| Patellofemoral osteophyte | Gold standard | 0.25 (−0.05, 0.55; 58%) | 0.48 (0.26, 0.69; 62%) | 0.3 (−0.07, 0.67; 58%) | 0.53 (0.25, 0.81; 62%) | 0.17 (−0.17, 0.5; 50%) | 0.4 (0.08, 0.72; 50%) |
| Reader 1 | 0.43 (0.13, 0.74; 73%) | 0.46 (0.19, 0.73; 64%) | 0.44 (0.17, 0.71; 69%) | 0.6 (0.39, 0.81; 73%) | 0.28 (−0.07, 0.63; 62%) | 0.37 (0.09, 0.66; 62%) | |
| Reader 2 | 0.44 (0.17, 0.71; 69%) | 0.6 (0.39, 0.81; 73%) | 0.7 (0.4, 1; 77%) | 0.71 (0.37, 1; 78%) | 0.67 (0.42, 0.91; 77%) | 0.81 (0.6, 1; 86%) | |
| Reader 3 | 0.28 (−0.07, 0.63; 62%) | 0.37 (0.09, 0.66; 62%) | 0.67 (0.42, 0.91; 77%) | 0.81 (0.6, 1; 86%) | 0.51 (0.09, 0.92; 77%) | 0.84 (0.52, 1; 89%) | |
Intrareader reliability is found by comparing the same reader in the column and the row (for example, comparing the “Reader 1” row with the “Reader 1” column). Interreader reliability is found by comparing different readers in the column and row (for example, comparing the “Reader 1” column with the “Gold standard” row gives the interreader reliability between reader 1 and the radiologist). Gold standard is the reading of the experienced radiologist. KL: Kellgren-Lawrence grade.