Table 4. Assessing the Association of 8-Week Pain Trajectory With 6-Month Knee Injury and Osteoarthritis Outcome Score (KOOS) Pain Scoresa.
| Variable | Final Model 6-mo KOOS Pain Score (95% CI)b | P Value |
|---|---|---|
| Pain trajectory 8 wk after total knee arthroplasty | ||
| Fast pain responders | 1 [Reference] | NA |
| Slow pain responders | –11.3 (–13.9 to –8.7) | <.001 |
| Race | ||
| White | 1 [Reference] | NA |
| Nonwhite | –6.6 (–11.6 to –1.5) | .01 |
| Charlson Comorbidity Index Score | ||
| 0 | 1 [Reference] | NA |
| 1 | –1.3 (–4.1 to 1.5) | .36 |
| 2 | –1.7 (–5.9 to 2.5) | .42 |
| ≥3 | –6.8 (–11.8 to –1.8) | .008 |
| Preoperative SF-36, with 1-unit increase | ||
| PCS score | 0.3 (0.1 to 0.4) | <.001 |
| MCS score | 0.3 (0.2 to 0.4) | <.001 |
Abbreviations: MCS, mental component summary; NA, not applicable; PCS, physical component summary; SF-36, 36-Item Short Form Health Survey.
a
The reduced 6-month model included pain trajectory, race, Charlson Comorbidity Index, and preoperative SF-36 PCS score and MCS score.
b
Because the R2 value for the reduced model was the same as for the full model that included all the factors based on the principle of parsimony, reduced models were more desirable. No evidence of multicollinearity was found because the variance inflation factors for each of the variables were 1.08 or lower (a variable for which variance inflation factor values are greater than 10 may merit further investigation). The adjusted R2 was 0.2