Table 1.

Baseline characteristics of participants in the analysis of the association between baseline synovitis and the risk of incident OA at both knee and hand sites over three years of follow-up.

	Participants without RKOAa	Participants without SKOAb	Participants without RHOAc	Participants without SHOAd
Participants (knees or hands), n	2211 (3951 knees)	2420 (4600 knees)	2280 (4022 hands)	2600 (5016 hands)
Women, n (%)	1189 (53.8%)	1336 (55.2%)	1325 (58.1%)	1496 (57.5%)
Age, years (mean ± SD)	62.7 ± 8.4	63.3 ± 8.5	62.8 ± 8.3	63.7 ± 8.6
BMI, kg/m2 (mean ± SD)	24.0 ± 3.4	24.0 ± 3.4	24.1 ± 3.5	24.1 ± 3.5
Smoking status (%)
Non-smoker	62.0	63.5	65.3	65.4
Ex-smoker	4.6	4.5	4.2	4.4
Current smoker	33.4	32.0	30.5	30.2
Alcohol drinking (%)
Non-drinker	52.1	52.3	53.3	53.7
Ex-drinker	10.3	10.6	9.8	10.8
Current drinker	37.6	37.1	36.9	35.5
Joint injury history (%)e	3.0	2.9	4.3	4.6
Education (educated, %)f	72.8	71.0	69.9	68.8
Physical activity level (high, %)	85.2	85.6	85.6	85.0
Synovitis (%)	7.0	8.4	8.9	13.7

n, number; SD, standard deviation; BMI, body mass index; OA, osteoarthritis; RKOA, radiographic knee OA; SKOA, symptomatic knee OA; RHOA, radiographic hand OA; SHOA, symptomatic hand OA.

^aParticipants who underwent baseline knee joint ultrasound assessment without pre-existing RKOA at the joint level.

^bParticipants who underwent baseline knee joint ultrasound assessment without pre-existing SKOA at the joint level.

^cParticipants who underwent baseline hand joint ultrasound assessment without pre-existing RHOA at the joint level.

^dParticipants who underwent baseline hand joint ultrasound assessment without pre-existing SHOA at the joint level.

^eJoint injury history was defined as a history of joint injury severely restricting function for at least one week.

^fEducated was defined as primary school or above.