Table 2.

Psychometric properties at baseline and 1 year after primary hip joint replacement

		Baseline				1 year after surgery
	Number of items	N	% Floor5	%Ceiling6	Cronbach's α7	N	% Floor5	%Ceiling6	Cronbach's α7
Brief Pain Inventory
Pain severity index1	4	232	0	1	0.88	200	21	0	0.91
Function interference index2	7	234	0.4	1.3	0.87	191	24	0	0.95
WOMAC 3
Pain	5	247	0.4	1.6	0.79	203	37	0	0.87
Stiffness	2	247	0.8	4.0	0.70	203	28	0	0.84
Physical function	17	248	0	0	0.93	202	9	0	0.96
SF-36 Scale4
Physical functioning	10	248	4	0	0.82	201	1	4	0.92
Role-physical	4	247	82	4	0.84	197	37	34	0.89
Bodily pain	2	250	6	0	0.68	200	0.5	27	0.87
General health	5	240	0.8	3	0.69	196	0	7	0.81
Vitality	4	242	3	0	0.82	199	0	4	0.86
Social functioning	2	250	4	18	0.82	202	0.5	56	0.89
Role-emotional	3	242	42	40	0.91	198	23	60	0.89
Mental health	5	240	0	7	0.85	198	0	12	0.78

¹ Range 0 - 40 (no pain, pain as bad you can image)

² Range 0 - 70 (does not interfere, interferes completely)

³ Range 0 - 10 (no problem, maximum problem)

⁴ Range 0 - 100 (poor health status, maximal health status)

⁵ % scoring worst possible value

⁶ % scoring best possible value

⁷ Internal consistency reliability