Table 1.
Characteristics of all study participants, stratified by self-reported bilateral knee pain and back pain (N = 1,252)
| Characteristics, n% | ALL Sample N = 1,252 |
No bilateral knee pain and no back pain N = 283 (23%) |
No bilateral knee pain and back pain N = 227 (18%) |
Bilateral knee pain and no back pain N = 238 (19%) |
Bilateral knee and back pain 504 (40%) |
P value |
|---|---|---|---|---|---|---|
| Sex | 0.16 | |||||
| Men | 511 (41) | 128 (45) | 95 (42) | 100 (42) | 188 (37) | |
| Women | 741 (59) | 155 (55) | 132 (58) | 138 (58) | 316 (63) | |
| Race | <0.0001 | |||||
| White/Caucasians | 1,057 (84) | 258 (91) | 204 (90) | 190 (80) | 405 (80) | |
| Others (Blacks/Asians/non- whites) |
195 (16) | 25 (9) | 23 (10) | 48 (20) | 99 (20) | |
| Education | 0.60 | |||||
| <High school | 266 (21) | 59 (21) | 42 (18) | 56 (24) | 109 (22) | |
| ≥High school | 986 (79) | 224 (79) | 185 (82) | 182 (76) | 395 (78) | |
| Income per year in US dollars($) | 0.067 | |||||
| <$50,000 | 620 (50) | 124 (44) | 107 (47) | 129 (54) | 260 (52) | |
| >$50,000 | 632 (50) | 159 (56) | 120 (53) | 109 (46) | 244 (48) | |
| Co-morbidity | 0.08 | |||||
| ≥1 | 389 (31) | 82 (29) | 61 (27) | 69 (29) | 327 (65) | |
| 0 | 863 (69) | 201 (71) | 166 (73) | 169 (71) | 177 (35) | |
| Depressive symptoms (CESD) | 0.010 | |||||
| Yes | 78 (6) | 8 (3) | 12 (5) | 23 (10) | 35 (7) | |
| No | 1,174 (94) | 275 (97) | 215 (95) | 215 (90) | 469 (93) | |
|
| ||||||
| Characteristics, mean ± SD | ||||||
|
| ||||||
| Age in years | 71.3 ± 3.9 | 71.6 ± 4.0 | 71.8 ± 4.0 | 71.3 ± 3.7 | 70.8 ± 4.0 | 0.0025 |
| BMI (kg/m2) | 28.0 ± 4.1 | 27.4 ± 3.9 | 27.5 ± 4.0 | 28.3 ± 4.2 | 28.8 ± 4.6 | <0.0001 |
|
| ||||||
| Self-reported quality of life, mean ± SD | ||||||
|
| ||||||
| SF-12, PCS | 48.5 ± 7.9 | 53.0 ± 6.0 | 49.6 ± 7.3 | 46.1 ± 8.9 | 45.4 ± 9.4 | <0.0001 |
| SF-12, MCS | 55.3 ± 6.8 | 56.2 ± 5.6 | 55.3 ± 6.4 | 55.3 ± 7.5 | 54.6 ± 7.9 | 0.028 |
Abbreviations: BMI, body mass index; PCS, physical composite scale; MCS, mental composite scale; SD, standard deviation; CESD, Center for Epidemiological Studies Depression Scale; SF-12, Medical health survey short form-12.