Table 3.

Comparison of reliability and validity of smartphone and visual estimation measurements against universal goniometer measurements within observers (intraobserver reliability)

Movement / method	ICC (95% CI)	Mean absolute difference ± sd (°)	Bland–Altman mean difference (95% CI) (°)	± 95% LOA (°)	P value*
Flexion
Visual estimation	0.92 (0.77–0.96)	7.7 ± 5.9	4.5 (3.0–5.9)3.04–5.89	± 12.5	< 0.001
Smartphone	0.98 (0.97–0.99)	2.6 ± 1.9	0.3 –(–0.4–0.9)-0.43–0.95	± 6.1	0.450
Extension
Visual estimation	0.98 (0.97–0.99)	2.9 ± 3.3	0.7 (–0.1–1.4)-0.13–1.43	± 3.5	0.102
Smartphone	0.99 (0.98–0.99)	1.1 ± 1.0	–0.2 (–0.3–0.3)-0.32–0.27	± 2.6	0.867
Supination
Visual estimation	0.97 (0.96–0.98)	3.9 ± 3.3	0.5 (–0.4–1.4)-0.44–1.44	± 8.3	0.295
Smartphone	0.99 (0.98–0.99)	2.2 ± 1.5	0.7 (0.2–1.2)0.19–1.21	± 4.5	0.108
Pronation
Visual estimation	0.91 (0.86–0.94)	4.8 ± 3.5	0.4 (–0.9–1.7)-0.95–1.67	± 11.5	0.008
Smartphone	0.98 (0.97–0.99)	1.9 ± 1.1	–0.1 (–0.6–0.4)-0.64–0.37	± 4.4	0.589

CI, confidence interval; ICC, intraclass correlation coefficient; LOA, limits of agreement

^*P values calculated via paired-T test for mean absolute differences. Significance set at α = 0.05