Table 3. Factors Associated With 6-Month Knee Injury and Osteoarthritis Outcome Score (KOOS) Pain Scores in Univariate Analysesa.
| Variable | KOOS Pain Score, Mean (SD) | P Value |
|---|---|---|
| Pain trajectory 8 wk after total knee arthroplasty | ||
| Fast pain respondersb | 87.3 (13.4) | <.001 |
| Slow pain respondersc | 74.5 (19.4) | |
| Sex | ||
| Male | 84.4 (17.4) | .16 |
| Female | 83.4 (15.7) | |
| Age, y | ||
| <65 | 82.2 (18.8) | .43 |
| ≥65 | 84.5 (14.9) | |
| BMI | ||
| <25 | 85.9 (13.6) | .08 |
| 25-29.9 | 82.9 (17.2) | |
| 30-34.9 | 84.7 (16.4) | |
| 35-39.9 | 80.9 (16.9) | |
| ≥40 | 87.0 (14.3) | |
| Race | ||
| White | 84.3 (15.8) | .01 |
| Nonwhite | 75.4 (22.2) | |
| Annual household income, $ | ||
| ≤45 000 | 82.3 (18.5) | .17 |
| >45 000 | 85.3 (14.6) | |
| Charlson Comorbidity Index | ||
| 0 | 85.4 (15.5) | <.001 |
| 1 | 82.5 (17.3) | |
| 2 | 80.1 (17.5) | |
| ≥3 | 74.7 (16.3) | |
| Preoperative SF-36 MCS score | ||
| <45 | 75.9 (19.3) | <.001 |
| ≥45 | 85.7 (14.8) |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); MCS, mental component summary; SF-36, 36-Item Short Form Health Survey.
Kruskal-Wallis test was used for the categorical variables in the table.
Patients who experienced pain relief in the immediate postoperative period are referred to as fast pain responders. The mean (SD) preoperative KOOS pain score for this subgroup was 49.2 (17.5), which was not different from the 46.4 (18.0) of slow pain responders. The improvement from preoperative to 6-month KOOS pain scores was 38.1 (19.2) in fast pain responders vs 28.1 (21.0) in slow pain responders.
Patients who experienced minimal pain relief in the immediate postoperative period are referred to as slow pain responders.