A review of the foot function index and the foot function index – revised

Table 11 Reliability and unidimensionality of the full scale, short form, and subscales

	Full scale	Short form	1-11	12-19	20-39	40-49	50-68
	(68 items)	(34 items)	(Pain)	(Stiffness)	(Difficulty)	(Limitation)	(Social issues)
Person Reliability	.96	.95	.89	.89	.94	.78	.84
Cronbach’s Alpha	.98	.97	.93	.95	.97	.87	.94
Unidimensionality Criteria (Ratio of the raw variance explained by measures: Unexplained variance in 1^st contrast ≥ 3)	56.8/10.6=	60.2/15.8=	66.7/22.1=	67.5/34.7=	72.7/15.5=	63.4/19.2=	53.6/18.1=
	5.4	3.8	3.0	1.94¹	4.69	3.3²	2.96³
	Yes	Yes	Yes	No	Yes	Yes	No

¹ Further inspection of the data revealed that the two-factor solution was associated with the severity of the items, where the two factors were actually low and high severity stiffness, i.e. opposite poles of the same factor. Therefore, the scale is useful as a measure of stiffness. ² These were the results after removing item 41 (ASSISTO).
³ Approximately unidimensional.

ISSN: 1757-1146