Table 2. Cumulative probability of osteoarthritis progression according to mitochondrial DNA (mtDNA) haplogroups and results of the extended Cox proportional hazard model.

	KL grade			JSN			Osteophytes			Subchondral sclerosis
Variables	N(%Progressors)¥	HR	95% CI#	N(%Progressors)¥	HR	95% CI#	N(%Progressors)¥	HR	95% CI#	N(%Progressors)¥	HR	95% CI#
Gender (male)		0.672	0.528–0.859*		1.006	0.755–1.335		0.843	0.650–1.081		1.021	0.791–1.343
Age (years)		1.011	0.999–1.024		0.998	0.982–1.013		0.993	0.980–1.007		1.008	0.994–1.023
BMI (Kg/m2)		1.045	1.020–1.069*		1.052	1.021–1.084*		1.028	1.004–1.055*		1.027	0.996–1.056
Previous surgery		0.909	0.702–1.190		0.686	0.487–0.909		0.981	0.739–1.282		1.054	0.788–1.378
Worst knee at bl±		0.937	0.687–1.305		4.993	3.700–7.373*		1.799	1.405–2.314*		1.396	1.050–1.827*
mtDNA haplogroups
H (n = 341)	145 (42.5%)	1		111 (32.6%)	1		164 (48.0%)	1		136 (39.8%)	1
J (n = 89)	40 (44.3%)	1.147	0.731–1.655	28 (31.4%)	0.891	0.581–1.404	45 (51.1%)	1.090	0.715–1.611	29 (32.5%)	0.764	0.487–1.230
Uk (n = 228)	100 (44.1%)	0.986	0.760–1.356	64 (28.4%)	0.741	0.530–1.049	106 (46.8%)	0.906	0.684–1.203	66 (29.1%)	0.632	0.436–0.879
T (n = 85)	19 (22.0%)	0.499	0.261–0.819*	17 (19.7%)	0.547	0.280–0.900*	25 (29.0%)	0.573	0.304–0.893*	21 (25.0%)	0.549	0.295–0.884*
Others (n = 148)	53 (36.0%)	0.786	0.542–1.099	35 (23.7%)	0.699	0.445–1.051	50 (34.1%)	0.687	0.500–1.013	52 (35.1%)	0.847	0.563–1.220

KL: Kellgren and Lawrence; JSN: joint space narrowing; BMI: body mass index; bl: baseline; (^¥): cumulative osteoarthritis progression rate after 48 months of follow-up; HR: hazard ratio; CI: confidence interval; (#): confidence intervals for the hazard ratios obtained using the bootstrap methodology by the percentile method; (±): the worst knee at baseline refers to the radiological status of the knee attending to (highest) KL grade, JSN grade, osteophytes grade or sclerosis grade, as appropriate on each case; (*): statistical significance declared at p≤0.05.