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Table 3 Knee pain characteristics at each selection point.

From: The Knee Clinical Assessment Study – CAS(K). A prospective study of knee pain and knee osteoarthritis in the general population: baseline recruitment and retention at 18 months

  Responded to Regional Pains Survey Attended research clinic Responded to 18 m FUP Survey
N* 1949 819 776
Baseline knee pain chronicity:    
   Less than 7 days 180 (11) 61 (8) 58 (8)
   1–4 weeks 249 (15) 106 (14) 103 (14)
   1 mo to < 3 mo 252 (15) 117 (16) 111 (16)
   3 mo+ 1019 (60) 469 (62) 441 (62)
Baseline WOMAC: Mean (sd†)    
   Pain (0–20) 6.3 (4.5) 6.4 (4.4) 6.4 (4.4)
   Stiffness (0–8) 2.7 (2.0) 2.7 (1.9) 2.7 (1.9)
   Function (0–68) 21.1 (15.8) 20.9 (15.2) 20.7 (15.2)
Baseline radiographic knee OA¶:    
   Definite (any compartment)    
Yes   539 (68) 514 (69)
No   251 (32) 235 (31)
   Definite (patello-femoral) ¶:    
Yes   507 (64) 481 (64)
No   283 (36) 268 (36)
   Definite (tibia-femoral) ¶:    
Yes   350 (44) 332 (44)
No   440 (56) 417 (56)
   Severe (any compartment) ¶:    
Yes   313 (40) 293 (39)
No   477 (60) 456 (61)
Baseline symptomatic knee OA‡    
   Yes   260 (33) 242 (32)
   No   530 (67) 507 (68)
  1. Figures represent numbers and percentages unless otherwise stated
  2. * – individual items may not add to totals due to missing data
  3. † – sd = standard deviation
  4. ¶ – Baseline x-ray data is available for 790 participants at recruitment
  5. ‡ – Knee pain, aching or stiffness on most days in the last month plus definite radiographic osteoarthritis in the index knee