In knee osteoarthritis, what is the knee deformity threshold after which the ankle realigns beyond the neutral zone?

Table 5 Multivariable regression analyses of ankle alignment

Predictor	β (SE) or OR	95%CI	P value
Multivariable linear regression (outcome: TTA)
Intercept	-0.35 (11.22)1	-22.42 to 21.71	0.97
HKAA (per 1° increase)	0.49 (0.06)1	0.36 to 0.61	< 0.001a
Age (per year)	0.04 (0.03)1	-0.03 to 0.10	0.27
Sex (male vs female)	0.96 (0.69)1	-0.41 to 2.32	0.17
KL grade (per grade)	-0.66 (0.32)1	-1.29 to -0.02	0.04a
Multivariable logistic regression (outcome: Varus ankle malalignment)
Intercept	-	-	-
HKAA (per 1° increase)	0.792	0.71 to 0.87	< 0.001a
KL grade (per grade)	1.122	0.82 to 1.54	0.48
Age (per year)	0.982	0.95 to 1.02	0.34
Sex (male vs female)	0.322	0.17 to 0.62	< 0.001a

¹Data were showed as β (SE).

²Data were showed as OR.

^aP < 0.05 indicates statistical significance.

Linear regression coefficients (β) represent the mean change in tibiotalar angle (TTA; °) per unit increase in the predictor. OR represent the change in odds of varus ankle malalignment (TTA < 85.9°). All models were adjusted for age, sex, and Kellgren-Lawrence grade. KL: Kellgren-Lawrence; HKAA: Hip to knee to ankle angle; TTA: Tibiotalar angle.