TABLE I.
Baseline Sample Characteristics (N = 402)
| Baseline Characteristics | All (N = 402) | Usual Care (N = 137) | Arthritis Education (N = 135) | Pain Coping Skills (N = 130) |
| Age* (yr) | 63.2 ± 8.0 | 62.7 ± 7.7 | 64.2 ± 8.5 | 62.6 ± 7.9 |
| Female sex† | 267 (66%) | 88 (64%) | 85 (63%) | 94 (72%) |
| Body mass index* (kg/m2) | 32.3 ± 6.2 | 32.6 ± 6.5 | 31.7 ± 6.0 | 32.4 ± 6.1 |
| Race or ethnic group†‡ | ||||
| White | 249 (59%) | 86 (60%) | 83 (59%) | 80 (59%) |
| African American | 143 (34%) | 48 (34%) | 45 (32%) | 50 (37%) |
| Hispanic | 13 (3%) | 5 (3%) | 5 (4%) | 3 (2%) |
| Asian | 8 (2%) | 2 (1%) | 4 (3%) | 2 (1%) |
| Declined to answer§ | 6 (1%) | 2 (1%) | 4 (3%) | — |
| Current income† | ||||
| <$10,000 | 42 (10%) | 14 (10%) | 12 (9%) | 16 (12%) |
| $10,000 to $24,999 | 84 (21%) | 28 (20%) | 30 (22%) | 26 (20%) |
| $25,000 to $49,999 | 91 (23%) | 27 (20%) | 31 (23%) | 33 (25%) |
| $50,000 to $99,999 | 94 (23%) | 35 (26%) | 33 (24%) | 26 (20%) |
| ≥$100,000 | 53 (13%) | 18 (13%) | 16 (12%) | 19 (15%) |
| Declined to answer§ | 38 (10%) | 15 (11%) | 13 (10%) | 10 (8%) |
| Current work status† | ||||
| Employed | 132 (33%) | 45 (33%) | 42 (31%) | 45 (35%) |
| Not working in part due to health problems | 102 (25%) | 36 (26%) | 32 (24%) | 34 (26%) |
| Not working for other reasons | 167 (42%) | 56 (41%) | 60 (44%) | 51 (39%) |
| Declined to answer§ | 1 (0.2%) | — | 1 (1%) | — |
| Education† | ||||
| Less than high school | 26 (7%) | 10 (7%) | 8 (6%) | 8 (6%) |
| High school graduate | 91 (23%) | 35 (26%) | 33 (24%) | 23 (18%) |
| Some college | 103 (26%) | 40 (29%) | 31 (23%) | 32 (25%) |
| College degree or higher | 182 (45%) | 52 (38%) | 63 (47%) | 67 (52%) |
| Marital status† | ||||
| Married | 197 (49%) | 70 (51%) | 64 (47%) | 63 (49%) |
| Divorced | 80 (20%) | 26 (19%) | 26 (19%) | 28 (22%) |
| Never married | 49 (12%) | 19 (14%) | 10 (7%) | 20 (15%) |
| Widowed | 47 (12%) | 15 (11%) | 18 (13%) | 14 (11%) |
| Separated | 20 (5%) | 5 (4%) | 13 (10%) | 2 (2%) |
| Member of an unmarried couple | 7 (2%) | 1 (1%) | 3 (2%) | 3 (2%) |
| Declined to answer§ | 2 (1%) | 1 (1%) | 1 (1%) | — |
| Current smoker (yes)† | 47 (12%) | 19 (14%) | 12 (9%) | 16 (12%) |
| Health history | ||||
| Modified Charlson Comorbidity Index*# | 8.7 ± 4.1 | 8.8 ± 4.2 | 8.7 ± 4.0 | 8.7 ± 4.1 |
| Knee pain duration** (yr) | 6 (3 to 15) | 8 (3 to 20) | 6 (3 to 12) | 6 (3 to 12) |
| Opioid use at baseline† | 121 (30%) | 48 (35%) | 37 (27%) | 36 (28%) |
| Unicompartmental knee arthroplasty (yes)† | 17 (4%) | 8 (6%) | 5 (4%) | 4 (3%) |
| Psychological health* | ||||
| Patient Health Questionnaire (PHQ-8)†† | 6.0 ± 5.0 | 5.9 ± 5.2 | 6.1 ± 5.0 | 5.8 ± 4.8 |
| Generalized Anxiety Disorder Scale (GAD-7)‡‡ | 5.4 ± 4.9 | 5.6 ± 4.9 | 5.2 ± 5.1 | 5.3 ± 4.8 |
| Arthritis Self-Efficacy Scale*§§ | 49.1 ± 17.8 | 51.6 ± 18.5 | 50.4 ± 17.7 | 45.1 ± 16.7 |
| Primary outcome scores* | ||||
| WOMAC Pain Scale## (points) | 11.4 ± 3.4 | 11.4 ± 3.5 | 11.3 ± 3.5 | 11.6 ± 3.1 |
| Secondary outcome scores* | ||||
| WOMAC physical function*** | 37.2 ± 11.6 | 36.0 ± 11.1 | 37.1 ± 11.8 | 38.6 ± 11.8 |
| Numeric pain rating* | 6.1 ± 1.9 | 6.2 ± 1.9 | 6.0 ± 2.0 | 6.0 ± 1.8 |
| SPPB††† | 9.3 ± 2.9 | 9.7 ± 2.6 | 9.1 ± 2.9 | 9.1 ± 3.2 |
| 6-minute walk test (m) | 297 ± 120 | 309 ± 106 | 279 ± 132 | 305 ± 121 |
| PCS‡‡‡ (points) | 30.0 ± 9.3 | 29.7 ± 9.2 | 30.0 ± 9.2 | 30.4 ± 9.6 |
The values are given as the mean and the standard deviation.
The values are given as the number of patients, with the percentage in parentheses.
In the race or ethnic group category, the sums are greater than the total sample (n = 402) because some subjects marked >1 category. The sum may equal >100% because of multiple categories.
This category indicates not specified or missing.
The modified Charlson Comorbidity Index score range is 0 to 45 points; higher scores indicate greater comorbidity burden.
The values are given as the median, with the interquartile range in parentheses.
The PHQ-8 score range is 0 to 24 points; higher scores indicate more depressive symptoms.
The GAD-7 score range is 0 to 21 points; higher scores indicate more anxiety.
The Arthritis Self-Efficacy Scale score range is 0 to 80 points; higher scores indicate more self-efficacy.
The WOMAC Pain Scale score range is 0 to 20 points; higher scores indicate more function-limiting pain.
The WOMAC Physical Function Scale range is 0 to 68 points; higher scores indicate more difficulty with functional activities.
The Short Physical Performance Battery (SPPB) score range is 0 to 12 points; higher scores indicate better performance.
The Pain Catastrophizing Scale (PCS) range is 0 to 52 points; higher scores indicate more pain catastrophizing.