Table 3.
Accuracy of knee injection: influence of site and image-guidance—Relative and absolute risk difference*
| Knee injection site | Relative risk (95% confidence Interval) | Absolute risk difference (95% confidence interval) | Chi squared2, p-value |
|---|---|---|---|
| Medial midpatellar (guided vs blind) | 1.34 (1.15–1.57) | 0.22 (0.10–0.33) | 12.17, p = 0.0005 |
| Superomedial patellar (guided vs blind) | 1.22 (1.16–1.27) | 0.18 (0.14–0.22) | 72.03, p < 0.0001 |
| Anterolateral joint line (guided vs blind) | 1.39 (1.27–1.53) | 0.28 (0.20–0.35) | 30.03, p < 0.0001 |
| Lateral midpatellar (guided vs blind) | 1.14 (1.04–1.26) | 0.12 (0.001–0.20) | 3.91, p = 0.05 |
| Superolateral patellar (guided vs blind) | 1.15 (1.10–1.21) | 0.13 (0.10–0.18) | 14.73, p = 0.0001 |
| Lateral suprapatellar bursa (guided vs blind) | 1.18 (1.07–1.32) | 0.15 (0.08–0.26) | 35.44, p < 0.0001 |
| Medial knee injections as a group (guided vs blind) | 1.27 (1.21–1.32) | 0.21 (0.17–0.24) | 92.13, p < 0.0001 |
| Lateral knee injections as a group (guided vs blind) | 1.22 (1.17–1.26) | 0.17 (0.14–0.20) | 101.48, p < 0.0001 |
| Guided vs Blinded injections as a group | 1.24 (1.21–1.27) | 0.19 (0.17–0.21) | 124.54, p < 0.0001 |
| Blinded knee injections: lateral vs medial as a group | 1.05 (1.00–1.12) | 0.04 (0.00–0.08) | 3.75, p = 0.05 |
| Guided knee injections: lateral vs medial as a group | 1.01 (0.99–1.03) | 0.01 (−0.01 to 0.03) | 1.29, p = 0.3 |
⁎
Relative risk is the proportionate difference in accuracy of injections (between groups as defined in each row) while absolute risk difference is the absolute difference in accuracy.