Table 3.

WOMAC items fit statistics

	Location	Standard Error	Fit Residual	χ2	DF	Probability
Pain subscale items	-0.050	0.010	-4.110	6.990	2	0.030
Item 2 and 4 combined into a testlet 2. Going up or down stairs 4. Sitting or lying	0.010	0.010	1.430	0.240	2	0.885
1. Walking on a flat surface	0.050	0.010	0.260	0.100	2	0.953
3. At night while in bed	0.000	0.010	2.170	0.820	2	0.663
5. Standing upright	-0.050	0.010	-4.110	6.990	2	0.030
Physical Functioning subscale items
Item 1 and 5 combined into a testlet 1. Descending the stairs 5. Bending to floor	-0.350	0.006	4.267	6.574	2	0.037
2. Ascending the stairs	-0.101	0.009	1.135	0.466	2	0.792
3. Rising from sitting	-0.019	0.009	0.031	0.224	2	0.894
4. Standing	0.015	0.009	2.333	3.379	2	0.185
6. Walking on flat	0.065	0.009	1.055	0.020	2	0.990
7. Getting in/out of car	-0.035	0.009	-0.875	6.211	2	0.045
8. Going shopping	-0.024	0.009	-0.379	2.174	2	0.337
9. Putting on socks/stockings	-0.060	0.008	2.018	1.134	2	0.567
10. Rising from bed	0.034	0.008	0.146	7.781	2	0.020
11. Taking off socks/stockings	-0.021	0.008	-0.658	0.652	2	0.722
12. Lying in bed	0.112	0.008	1.606	1.334	2	0.513
13. Getting in/out of bath	-0.058	0.008	1.475	1.433	2	0.488
14. Sitting	0.194	0.009	0.467	2.195	2	0.334
15. Getting on/off toilet	0.132	0.008	0.290	2.405	2	0.300
16. Heavy domestic duties	-0.096	0.009	-1.238	8.452	2	0.015
17. Light domestic duties	0.212	0.009	0.433	0.371	2	0.831
Stiffness subscale items
1. How severe is your stiffness after first wakening in the morning?	-0.026	0.010	-0.674	4.113	2	0.128
2. How severe is your stiffness after sitting, lying or resting later in the day?	0.026	0.010	-0.418	4.495	2	0.106

* Pain subscale Bonferroni adjusted (0.05/5 items, p-value considered significant if <0.01); Physical Functioning subscale Bonferroni adjusted (0.05/17 items, p-value considered significant if <0.003); Stiffness subscale Bonferroni adjusted (0.05/17 items, p-value considered significant if < 0.025)