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Table 1 Characteristics of the study population (n = 186)

From: Elevated C-reactive protein is associated with lower increase in knee muscle strength in patients with knee osteoarthritis: a 2-year follow-up study in the Amsterdam Osteoarthritis (AMS-OA) cohort

  Baseline 2-year follow-up
  Number   Number  
Age, years 186 61 (7.3) - -
Female, n (%) 186 127 (68) - -
Radiographic OA-KL score ≥2, n (%) 184 130 (70) 186 123 (66)
WOMAC pain score, 0-20 183 7.9 (3.8) 185 7.0 (4.3)ª
WOMAC stiffness score, 0-8 179 3.7 (1.7) 186 3.5 (2.0)ª
WOMAC physical function score, 0-68 183 28.6 (13.4) 186 27.0 (15.3)
Comorbidities count, CIRS ≥2 184 0.8 (1.0) 175 1.1 (1.0)ª
NSAIDs, yes, n (%) 185 30 (16) 186 38 (20)
Body mass index, kg/m2 185 29.3 (5.5) 186 29.3 (5.4)
Physical activity ≥30 minutes, times per week - No information 183 3.0 (1.3)
PT treatment during the past 2 years, n (%) - No information 186 149 (80)
Knee muscle strengthb, Nm/kg 177 0.88 (0.4) 183 0.95 (0.4)ª
Inflammatory markers     
 C-reactive protein, mg/L 183   184  
 Median, IQR   2 (1-4)   2 (1-3)
 Mean, SD   3.4 (5.4)   2.9 (3.1)
 >3 mg/L, n (%)   50 (27)   45 (24)
 ESR, mm/hour 183   186  
 Median, IQR   9 (5-15)   7 (4-12)
 Mean, SD   11.6 (8.9)   9.5 (8.4)ª
 ≥20 mm/hour, n (%)   34 (18)   25 (13)
  1. Values are presented as mean ± standard deviation (SD), unless stated otherwise. ªSignificant difference between baseline and follow-up assessment (P <0.05). bMean quadriceps and hamstring muscles in osteoarthritis (OA) knees. CIRS, Cumulative Illness Rating Scale; ESR, erythrocyte sedimentation rate; IQR, interquartile range; KL, Kellgren-Lawrence; NSAID, non-steroidal anti-inflammatory drug; PT, physiotherapy; WOMAC, Western Ontario and McMaster Universities Osteoarthritis.