Table 1.

Baseline Characteristics of Participants With Chronic Low Back Pain
CharacteristicsaFacet Joint TrialSacroiliac Joint TrialCombination Trial
Intervention
(n = 125)
Control
(n = 126)
Intervention
(n = 116)
Control
(n = 112)
Intervention
(n = 103)
Control
(n = 99)
Age, mean (SD), y52.98 (11.48)52.60 (10.79)51.58 (10.94)51.13 (12.22)50.80 (11.33)53.31 (10.35)
Women, No. (%)65 (55.56)60 (51.72)87 (74.35)79 (75.96)64 (65.31)66 (74.15)
BMI, mean (SD)26.77 (5.17)27.62 (4.27)26.73 (4.17)26.76 (4.53)26.84 (3.82)26.43 (4.25)
Smoker, No. (%)34 (29.05)34 (29.05)29 (26.61)31 (29.81)23 (23.46)26 (29.21)
Education level, No. (%)b
Low57 (48.72)64 (55.17)59 (54.13)53 (50.96)52 (53.06)43 (48.31)
Moderate35 (29.99)34 (29.31)32 (29.36)32 (30.76)33 (33.67)32 (35.96)
High21 (17.95)16 (13.79)18 (16.51)18 (17.31)12 (12.24)14 (15.73)
Married or living with a partner, No. (%)93 (79.49)98 (84.48)85 (79.61)82 (79.61)66 (67.35)68 (76.40)
Having a paid job, No. (%)64 (54.70)66 (56.80)66 (60.55)50 (48.07)48 (48.97)44 (48.44)
History of back pain, median (IQR), mo
Time since first experience with low back pain146.00
(49.75-267.67)
100.33
(36.5-186.30)
97.33
(37.51-228.12)
65.08
(27.08-144.21)
120.58
(37.32-222.04)
97.33
(32.33-192.58)
Time since first current episode with low back pain31.33
(12.17-103.42)
26.73
(10.54-73.00)
30.33
(12.17-76.03)
24.33
(12.17-66.58)
36.50
(12.17-121.67)
32.33
(8.00-97.19)
Origin of back pain, No.
Facet and sacroiliac joint6970
Facet and disc1818
Sacroiliac joint and disc61
Facet and sacroiliac joint and disc36
Unknown74
CEQ score, mean (SD)c
Credibility21.36 (3.92)19.47 (5.49)21.36 (4.51)19.88 (5.31)20.10 (4.70)17.07 (5.99)
Expectancy18.97 (4.59)17.36 (5.20)18.75 (4.99)18.23 (5.31)16.88 (5.78)14.38 (6.24)
Pain intensity score in the past week, mean (SD)d7.14 (1.38)7. 19 (1.29)7.17 (1.65)7.06 (1.43)7.19 (1.43)7.43 (1.41)
Functioning score, mean (SD)e35.07 (14.66)34.39 (12.24)38.07 (14.07)33.70 (14.43)39.06 (14.03)37.20 (13.74)
Quality-of-life score, mean (SD)f0.52 (0.26)0.54 (0.26)0.50 (0.27)0.56 (0.27)0.49 (0.28)0.52 (0.28)
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); CEQ, credibility expectancy questionnaire.

aResults are presented of the 233 participants in the facet joint trial, 207 participants in the sacroiliac joint trial, and 187 participants in the combination trial who had complete baseline data.
bEducation levels: low indicates preschool, primary school, or lower secondary school; moderate indicates higher secondary school or undergraduate; high indicates tertiary, university, or postgraduate.
cA higher score indicates more credibility in the effectiveness of treatment or higher expectations about the treatment (score range, 0-27).
dMeasured by numeric rating scale (score range, 0-10); a higher score indicates more severe pain intensity.
eMeasured by Oswestry Disability Index (score range, 0-100); a higher score indicates worse functioning.
fMeasured by EuroQol-5D (score range, 0-1); a higher score indicates better quality of life.