Table 1

Characteristics of the study population according to chronic knee pain

VariableWithout chronic knee pain (n=2131)Chronic knee pain (n=527)P value
PHQ-9, n (%)
<102021 (94.8)436 (82.7)<0.0001
≥10110 (5.2)91 (17.3)
Levels of depressive symptom, n (%)
 None (PHQ-9 ≤4)1780 (83.5)303 (57.5)<0.0001
 Mild (5–9)241 (11.3)133 (25.2)
 Moderate (10–14)66 (3.1)51 (9.7)
 Moderately severe (15–19)33 (1.6)28 (5.3)
 Severe (≥20)11 (0.5)12 (2.3)
Age, years (mean±SD)61.2±8.666.1±9.1<0.0001
Age, n (%)
 50–59 years845 (39.7)111 (21.1)<0.0001
 60–69 years698 (32.8)182 (34.5)
 ≥80 years588 (27.6)234 (44.4)
Sex, n (%)
 Male1002 (47)117 (22.2)<0.0001
 Female1129 (53)410 (77.8)
BMI, kg/m2 (mean±SD)23.9±3.124.3±3.30.0533
Obesity, n (%)
 Underweight (≤18.5 kg/m2)55 (2.6)13 (2.5)0.2473
 Normal (18.5–24.9 kg/m2)1365 (64.1)300 (57)
 Obese (≥25 kg/m2)711 (33.4)213 (40.5)
Smoking status, n (%)
 Non-smoker1265 (60.4)383 (75)<0.0001
 Ex-smoker496 (23.7)78 (15.3)
 Current smoker334 (15.9)50 (9.8)
Alcohol consumption, n (%)
 None805 (38.4)235 (45.7)<0.0001
 One drink/month or less516 (24.6)156 (30.4)
 Two drinks/ month to three drinks/week585 (27.9)93 (18.1)
 Four drinks/ week or more193 (9.2)30 (5.8)
Occupation, n (%)
 Unemployed (student, housewife, etc)1003 (47.1)328 (62.2)<0.0001
 Office work/sales and services463 (21.8)53 (10.1)
 Agriculture, forestry and fishery186 (8.7)50 (9.5)
 Machine fitting and simple labour477 (22.4)96 (18.2)
Household income, n (%)
 Low546 (25.7)232 (44.3)<0.0001
 Low–moderate589 (27.7)136 (26)
 Moderate–high/high989 (46.6)156 (29.8)
Educational level, n (%)
 ≤6 years805 (37.8)345 (65.5)<0.0001
 7–9 years396 (18.6)73 (13.9)
 ≥10 years928 (43.6)109 (20.7)
Aerobic physical activity, n (%)
 No1100 (52.0)313 (60.5)0.0005
 Yes1016 (48.0)204 (39.5)
Duration of sleep, hours6.7±1.46.4±1.70.0026
Comorbidities, n (%)
 Hypertension765 (35.9)262 (49.7)<0.0001
 Dyslipidaemia413 (19.4)145 (27.5)0.0002
 Stroke77 (3.6)38 (7.2)0.0002
 Myocardial infarction31 (1.5)13 (2.5)0.2165
 Angina64 (3)17 (3.2)0.698
 Arthritis252 (11.8)285 (54.1)<0.0001
 Asthma56 (2.6)33 (6.3)<0.0001
 Diabetes mellitus304 (14.3)86 (16.3)0.7091
  • The Rao-Scott χ2 test or t-test was performed to determine differences between groups with/without chronic knee pain. Missing values/non-responses were excluded from analysis. Individuals with PHQ-9 scores >10 were considered to have depressive symptoms. Levels of depressive symptom were divided into five quartiles: none (0–4), mild (5–9), moderate (10–14), moderately severe (15–19) and severe (20–27) according to the PHQ-9 score. Continuous variables are presented as mean and SD, and categorical variables are presented as frequency and percentage.

  • BMI, body mass index; PHQ-9, Patient Health Questionnaire-9.