Test-retest reproducibility of elbow goniometric measurements in a rigid double-blinded protocol: Intervals for distinguishing between measurement error and clinical change

Increasingly, goniometry of elbow motion is used for qualification of research results. Expression of reliability is in parameters not suitable for comparison of results. We modified Bland and Altman's method, resulting in the smallest detectable differences (SDDs). Two raters measured elbow excursions in 42 individuals (144 ratings per test person) with an electronic digital inclinometer in a classical test-retest crossover study design. The SDDs were 0 ± 4.2° for active extension; 0 ± 8.2° for active flexion, both without upper arm fixation; 0 ± 6.3° for active extension; 0 ± 5.7° for active flexion; 0 ± 7.4° for passive flexion with upper arm fixation; 0 ± 10.1° for active flexion with upper arm retroflexion; and 0 ± 8.5° and 0 ± 10.8° for active and passive range of motion. Differences smaller than these SDDs found in clinical or research settings are attributable to measurement error and do not indicate improvement.