Does parallel item content on WOMAC's Pain and Function Subscales limit its ability to detect change in functional status?

Table 4 Correlation Coefficients (95% CI) Between Shortened Measures and WOMAC Pain and Physical Function Scores

Assessment	SIMILAR-8	DISSIMILAR-8	Difference Comparison (Z, p-value)
WOMAC Pain
Preoperative	0.83 (0.76, 0.88)	0.69 (0.57, 0.78)	4.04, p₂ < 0.001
1^st Postoperative	0.78 (0.69, 0.85)	0.66 (0.54, 0.76)	2.82, p₂ = 0.005
2^nd Postoperative	0.89 (0.84, 0.92)	0.66 (0.54, 0.75)	6.21, p₂ < 0.001
WOMAC Physical Function
Preoperative	0.94 (0.91, 0.96)	0.97 (0.95, 0.98)	2.43, p₂ = 0.015
1^st Postoperative	0.94 (0.91, 0.96)	0.95 (0.93, 0.97)	1.63, p₂ = 0.104
2^nd Postoperative	0.91 (0.87, 0.94)	0.95 (0.93, 0.97)	3.58, p₂ < 0.001

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