Table 4 Comparison of observed subgroup characteristics that are in line with proposed underlying phenotype with other subgroups (research question 2; findings resulting in accepted hypotheses in bold)
| Â | Low muscle strength subgroup (L) | High muscle strength subgroup (H) | Obesity subgroup (O) | Difference between L and H | Difference between L and O | Difference between H and O |
|---|---|---|---|---|---|---|
Baseline variables | ||||||
 Gender (female), n (%) | 310 (74%) | 88 (41%) | 388 (67%) | P < 0.001 | P = 0.03 | P < 0.001 |
 Age (years), mean ± SD | 65.2 ± 8.4 | 62.3 ± 8.6 | 62.7 ± 8.3 | P < 0.001 | P < 0.001 | P = 0.55 |
 Radiographic severity: | ||||||
  K&L grade 0/1, n (%) | 95 (24%) | 72 (35%) | 128 (24%) | P = 0.02* | P = 0.44 | P < 0.001* |
  K&L grade 2, n (%) | 131 (33%) | 64 (31%) | 145 (27%) |  |  |  |
  K&L grade 3, n (%) | 92 (23%) | 48 (23%) | 137 (25%) |  |  |  |
  K&L grade 4, n (%) | 83 (21%) | 42 (12%) | 132 (24%) |  |  |  |
 Knee surgery, n (%) | 51 (40%) | 24 (63%) | 65 (42%) | P = 0.01 | P = 0.80 | P = 0.02 |
 Nr. of comorbidities: | ||||||
  0, n (%) | 142 (62%) | 97 (71%) | 151 (43%) | P = 0.02 | P < 0.001 | P < 0.001 |
  1, n (%) | 61 (15%) | 28 (21%) | 105 (30%) |  |  |  |
  2. n (%) | 13 (3%) | 8 (6%) | 52 (15%) |  |  |  |
   ≥ 3, n (%) | 14 (3) | 3 (2%) | 41 (12) |  |  |  |
Outcome variables | ||||||
 Knee pain (0–10), mean ± SD | 5.6 ± 2.0 | 4.7 ± 2.2 | 5.8 ± 2.1 | P < 0.001 | P = 0.31 | P < 0.001 |
 Physical function (WOMAC, 0–68), mean ± SD | 43.6 ± 17.3 | 30.6 ± 18.2 | 48.7 ± 18.6 | P < 0.001 | P < 0.001 | P < 0.001 |
Stratification variables | ||||||
 Body mass index (kg/m2), mean ± SD | 26.4 ± 2.5 | 25.8 ± 2.4 | 35.5 ± 5.0 | P < 0.01 | P < 0.001 | P < 0.001 |
 Quad. strength (Nm/kg), mean ± SD | 0.71 ± 0.31 | 1.62 ± 0.32 | 0.78 ± 0.48 | P < 0.001 | P = 0.03 | P < 0.001 |
 30s-CST (repetitions), mean ± SD | 8.5 ± 2.3 | 13.2 ± 1.2 | 9.0 ± 2.7 | P < 0.001 | P = 0.15 | P < 0.001 |