Association between ultrasound-detected synovitis and knee pain: a population-based case–control study with both cross-sectional and follow-up data

Table 1 Characteristics of the study population

	No knee pain	Early knee pain	Established knee pain	p value
N	94	298	103
Age (years), mean (SD)	60.98 (9.81)	61.42 (9.66)	59.53 (10.04)	0.2992*
Women, n (%)	58 (61.70)	179 (60.07)	63 (61.17)	0.9509**
BMI (kg/m²), mean (SD)	26.78 (4.49)	28.85 (5.70)	31.96 (6.49)	< 0.0001*
Pain severity (NRS 0–10)^a, mean (SD)		4.55 (2.52)	7.40 (2.14)	< 0.0001^†
Global X-ray score (mm, 0–60), mean (SD)	2.24 (3.08)	5.72 (7.00)	11.28 (9.26)	< 0.0001*
Radiographic OA, n (%)	7 (7.45)	80 (26.85)	49 (47.57)	< 0.0001**
Muscle strength^b, n (%)
Quadriceps strength (kg, lowest tertile)	33 (35.11)	99 (33.22)	65 (63.11)	< 0.0001**
Hip abductor strength (kg, lowest tertile)	33 (35.11)	119 (39.93)	68 (66.02)	< 0.0001**
Use of analgesics, n (%)
Prescribed NSAIDs	3 (3.19)	19 (6.38)	15 (14.56)	0.0018
Opioids	3 (3.19)	44 (14.77)	22 (21.36)	0.0005
Over-the-counter NSAIDs	12 (12.77)	68 (22.82)	32 (31.07)	0.0021

Groups matched by age and gender. p values adjusted for multiple testing using the bootstrap method
SD standard deviation, NRS numerical rating scale, BMI body mass index, OA osteoarthritis, NSAID non-steroidal anti-inflammatory drug
^† t test
*Test for linear trend
**Cochran–Armitage test for trend
^aAverage pain severity in the past month
^bLowest tertile values for muscle strength tests: quadriceps strength < 17.6 kg for men and < 10.7 kg for women; hip abductor strength < 12.8 kg and < 8.2 kg, respectively

ISSN: 1478-6362