Demographic and disease characteristics in CHECK and selections of the OAI
| CHECK | OAI incidence cohort | p Value | CHECK knee subgroup | OAI incidence subgroup | p Value | |
| N | 1002 | 3285 | NA | 829 | 1578 | NA |
| Age in years | 56 (52–60) | 61 (53–69) | <0.001 | 56 (52–60) | 56 (51–61) | 0.8 |
| Gender, female | 79% | 59% | <0.001 | 80% | 64% | <0.001 |
| BMI, kg/m2 | 26 (23–28) | 28 (25–31) | <0.001 | 26 (24–28) | 28 (25–32) | <0.001 |
| Educational level | ||||||
| Primary school | 3% | 3% | 3% | 2% | ||
| Secondary school | 70% | 65% | 0.1 | 71% | 65% | 0.006 |
| High professional education/university | 27% | 32% | 26% | 33% | ||
| Site of pain | ||||||
| Knee only | 41% | 37% | 50% | 43% | ||
| Hip only | 17% | 7% | <0.001 | NA | NA | 0.002 |
| Knee and hip | 42% | 48% | 50% | 57% | ||
| No hip or knee pain | NA | 37% | NA | NA | NA | NA |
| Pain intensity (range 0–10) | 3 (3–5) | 2 (0–3) | <0.001 | 3 (2–5) | 2 (0–4) | <0.001 |
| K&L rating score for knee | ||||||
| Grade 0 | 68% | 14% | 65% | 19% | ||
| Grade 1 | 25% | 46% | 27% | 50% | ||
| Grade 2 | 6% | 16% | <0.001 | 7% | 16% | <0.001 |
| Grade 3 | 1% | 19% | 1% | 13% | ||
| Grade 4 | NA | 5% | NA | 2% | ||
| K&L rating score for hip | ||||||
| Grade 0 | 79% | NA | NA | 83% | NA | NA |
| Grade 1 | 15% | NA | NA | 13% | NA | NA |
| Grade 2 | 5% | NA | NA | 4% | NA | NA |
| Grade 3 | 1% | NA | NA | 0% | NA | NA |
| WOMAC subscales | ||||||
| Pain (range 0–20) | 5 (2–7) | 1 (0–3) | <0.001 | 5 (2–7) | 1 (0–3) | <0.001 |
| Stiffness (range 0–8) | 3 (2–4) | 1 (0–2) | <0.001 | 3 (2–4) | 1 (0–2) | <0.001 |
| Physical function (range 0–68) | 14 (7–24) | 2 (0–8) | <0.001 | 14 (7–24) | 3 (0–9) | <0.001 |
| Present employment | ||||||
| Paid job/volunteer | 53% | 70% | <0.001 | 52% | 79% | <0.001 |
| No paid job | 47% | 30% | 48% | 21% | ||
| SF-36 subscales (range 0–100): | ||||||
| Physical function | 80 (65–90) | NA | NA | 75 (65–85) | NA | NA |
| Physical role | 100 (50–100) | NA | NA | 100 (38–100) | NA | NA |
| Bodily pain | 67 (57–80) | NA | NA | 67 (57–80) | NA | NA |
| Fatigue | 65 (55–75) | NA | NA | 65 (55–75) | NA | NA |
| Social function | 88 (63–100) | NA | NA | 88 (63–100) | NA | NA |
| Fear and depression | 100 (100–100) | NA | NA | 100 (100–100) | NA | NA |
| Mental health | 80 (68–88) | NA | NA | 80 (68–88) | NA | NA |
| PCS | 47 (40–51) | 53 (46–56) | <0.001 | 47 (40–51) | 53 (46–56) | <0.001 |
| MCS | 55 (50–59) | 55 (50–58) | 0.4 | 55 (50–59) | 55 (49–58) | 0.3 |
| EuroQol utility | 0.7 (0.7–0.8) | NA | NA | 0.7 (0.7–0.8) | NA | NA |
Median values with 25th–75th percentiles between brackets and categorical variables as percentages (%) are given. BMI, body mass index; K&L, Kellgren and Lawrence grade; MCS, mental component scale (in Cohort Hip and Cohort Knee; CHECK both scales calculated without general health scale); NA, not available/applicable; braces indicates statistical differences between the distribution of a parameters between both cohorts; OAI, Osteoarthritis Initiative; PCS, physical component scale; SF-36, Short Form 36-item health status survey questionnaire with higher score indicating a better health-related quality of life; WOMAC, Western Ontario and McMaster Universities osteoarthritis index with higher scores indicating worst health.