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

Table 4 Knee osteoarthritis severity-based differences in demographics and alignment

KL grade		1	2	3	4	P value	Effect size3
Age (year)		44.39 ± 9.65	52.72 ± 10.03	56.36 ± 8.16	60.19 ± 6.98	< 0.0011,a	NA
HKAA (°)		176.0 (173.0-178.0)	176.0 (173.0-179.0)	175.0 (172.0-178.0)	173.0 (169.0-177.0)	< 0.0011,a	NA
TTA (°)		87.0 (84.0-90.0)	86.0 (83.0-90.0)	85.0 (81.0-89.0)	83.0 (79.0-88.0)	< 0.0011,a	NA
Knee alignment	Varus	100 (11.8)	154 (18.2)	191 (22.6)	239 (28.3)	< 0.0012,a	0.12
	Neutral	31 (3.7)	36 (4.3)	30 (3.6)	22 (2.6)
	Valgus	2 (0.2)	12 (1.4)	13 (1.5)	15 (1.8)
Ankle alignment	Varus	53 (6.3)	91 (10.8)	127 (15)	188 (22.3)	< 0.0012,a	0.16
	Neutral	66 (7.8)	92 (10.9)	88 (10.4)	64 (7.6)
	Valgus	14 (1.7)	19 (2.3)	19 (2.3)	24 (2.8)

¹Continuous variables were compared using the Kruskal-Wallis.

²Categorical variables were compared using the Pearson χ² test.

³Effect size quantified using Cramér’s V, interpreted as negligible (< 0.10), small (0.10-0.19), moderate (0.20-0.39), or strong (≥ 0.40).

^aP < 0.05 indicates statistical significance.

Data were presented as n (%) or mean ± SD or median (interquartile range). KL: Kellgren-Lawrence; HKAA: Hip to knee to ankle angle; TTA: Tibiotalar angle; NA: Not applicable.