Table III.
Baseline characteristics of participants in the CAS-K analysis cohort (United Kingdom (2002–2003)) and the matched OAI sample (United States (2004–2006))
| CAS-K (N = 570) | OAI (N = 570) | |
|---|---|---|
| Age (years): mean (SD)∗ | 64 (8.0) | 64 (8.5) |
| Female gender∗ | 309 (54) | 296 (52) |
| BMI: mean (SD)∗ | 29.5 (5.0) | 29.4 (4.9) |
| Time since problem† onset | ||
| No knee pain for most days in a month | 143 (25) | |
| <1 year | 57 (10) | 63 (11) |
| 1–5 years | 201 (35) | 160 (28) |
| 5+ years | 312 (55) | 204 (36) |
| WOMAC function27: median (IQR)∗ | 17.0 (6.0, 30.0) | 18.0 (5.0, 30.0) |
| Kellgren–Lawrence score in tibiofemoral joint∗ | ||
| 0 | 308 (54) | 298 (52) |
| 1 | 54 (9) | 51 (9.0) |
| 2 | 82 (14) | 96 (17) |
| 3 | 70 (12) | 63 (11) |
| 4 | 56 (10) | 62 (11) |
| Baseline exclusion criteria in OAI | ||
| Bilateral total knee arthroplasty | 0 (0) | 0 (0) |
| Bilateral severe joint space narrowing | 22 (4) | 0 (0) |
| Unilateral total knee arthroplasty and contralateral severe joint space narrowing | 0 (0) | 0 (0) |
| Aged 80 years and over | 21 (4) | 0 (0) |
| Excessive weight for magnetic resonance imaging scan‡ | 10 (2) | 0 (0) |
| WOMAC pain27: median (IQR) | ||
| Baseline∗ | 5.0 (2.0, 9.0) | 5.0 (2.0, 9.0) |
| 12-months | N/A | 3.0 (1.0, 7.0) |
| 18-months | 5.0 (2.0, 9.0) | N/A |
| 24-months | N/A | 3.0 (1.0, 7.0) |
| 36-months | 6.0 (2.0, 10.0) | 3.0 (0.0, 7.0) |
| 48-months | N/A | 3.0 (0.0, 7.0) |
| 54-months | 5.0 (2.0, 9.0) | N/A |
| 60-months | N/A | 3.0 (0.0, 7.0) |
| 72-months | 6.0 (3.0, 10.0) | 3.0 (0.0, 7.0) |
Abbreviations: IQR, Inter-quartile range; N/A, Not applicable; SD, standard deviation; WOMAC, Western Ontario & McMaster Universities Osteoarthritis Index. Numbers are N (%) unless otherwise stated.
∗
Variable used in matching.
†
For CAS-K, onset relates to the current knee problem, for OAI, onset relates to knee pain, aching or stiffness experienced on most days or more in a month for either knee.
‡
Males >130 kg, females >114 kg.