The Shoulder Pain and Disability Index demonstrates factor, construct and longitudinal validity

Table 2 Results of Factor Analysis for SPADI on 3 occasions

	Baseline		3 months		6 months
Item	1	2	1	2	1	2
Pain at its worst	0.09	0.76	0.84	0.22	0.87	0.20
Pain when lying on involved side	0.24	0.82	0.85	0.24	0.88	0.22
Pain when reaching for something on a high shelf	0.33	0.81	0.85	0.31	0.88	0.30
Pain when touching the back of your neck	0.61	0.52	0.66	0.52	0.68	0.46
Pain pushing with involved arm	0.27	0.78	0.78	0.26	0.74	0.42
Difficulty washing your hair	0.76	0.40	0.39	0.82	0.44	0.79
Difficulty washing your back	0.69	0.44	0.51	0.72	0.50	0.65
Difficulty putting on an undershirt or pullover sweater	0.66	0.42	0.45	0.76	0.45	0.76
Difficulty putting on a shirt that buttons down the front	0.87	0.05	0.27	0.82	0.22	0.85
Difficulty putting on your pants	0.80	0.16	0.10	0.83	0.14	0.85
Difficulty placing an object on a high shelf	0.49	0.70	0.79	0.43	0.72	0.52
Difficulty carrying a heavy object of 10 pounds	0.47	0.61	0.61	0.53	0.55	0.56
Difficulty removing something from your back pocket	0.68	0.36	0.40	0.73	0.36	0.79

Extraction Method: Principal Component Analysis. Rotation Method: Varimax with Kaiser Normalization. Rotation converged in 3 iterations. The items falling into the "pain factor" are bolded and the items falling into the disability factor are underlined.