Table 2.

Knee pain prevalence, crude and adjusted analysis of the association between the outcome and selected variables among adolescents (n = 619) attending municipal schools in the city of Rio Grande, RS, Brazil, 2014.

Variable	Knee pain				Crude analysis	p-value	Adjusted analysis	p-value
	Yes		No		PR (95% CI)		PR (95% CI)
	N	%	n	%
Gender						0.63		0.74
Boys	55	21.6	199	78.4	1		1
Girls	85	23.3	280	76.7	1.08 (0.79–1.45)		1.05 (0.78–1.41)
Age						<0.01a		<0.01a
10–11 years	20	14.5	118	85.5	1		1
12–14 years	85	22.4	295	77.6	1.54 (0.99–2.41)		1.67 (1.07–2.58)
15–17 years	35	34.7	66	65.3	2.39 (1.47–3.88)		2.44 (1.51–3.94)
Skin color						0.12		0.29
White	86	20.8	328	79.2	1		1
Black/brown	54	26.3	151	73.7	1.26 (0.94–1.70)		1.17 (0.87–1.58)
Body mass index/age						0.6		0.54
Normal	92	23.5	300	76.5	1		1
Overweight	20	19.6	82	80.4	0.83 (0.59–1.28)		0.88 (0.57–1.37)
Obese	28	22.4	97	77.6	0.95 (0.65–1.38)		1.12 (0.76–1.66)
Physical education at school						0.01a		0.01a
No	17	37.8	28	62.2	1		1
Yes	123	21.4	451	78.6	0.57 (0.37–0.85)		0.54 (0.35–0.82)
Physical activity in leisure time						0.72		0.65
Insufficiently active	91	22.2	319	77.8	1		1
Active	49	23.4	160	76.6	1.05 (0.77–1.43)		1.07 (0.79–1.45)
Backpack weight						0.72		0.31
≤10% body weight	114	22.5	393	77.5	1		1
>10% body weight	26	24.1	82	75.9	1.07 (0.73–1.55)		1.21 (0.83–1.77)
Form of carrying backpack						0.77		0.91
Back	136	22.7	462	77.3	1		1
Arms/hands	4	20.0	16	80.0	0.88 (0.36–2.14)		1.05 (0.44–2.48)

PR (95% CI), prevalence ratio (95% CI). Multivariate analysis: 1st level – Demographic characteristics (age, gender, skin color); 2nd level – Biological determinants (nutritional status – BMI/age); School-associated factors (form of carrying backpack, backpack weight); 3rd level – Lifestyles (doing physical education at school, doing physical activities during leisure time).

^ap < 0.05.