© 2016 Hanley & Belfus Study Design Prospective cohort study. Purpose of the Study To compare the inter-rater reliability of using a modified finger goniometer (MFG) for the measurement of isolated forearm rotation for patients with distal radius fractures to the currently accepted technique for isolated forearm measurement. Introduction The currently accepted method of forearm measurement requires the assessor to visually estimate vertical for the stationary arm and placement of the moveable arm while placing a straight edge along a curved surface. Inter-rater reliability may be limited as assessors may estimate the placement of the goniometer arms differently depending on their experience, posture, and even their positioning relative to the patient. Rather than continue to place a straight edge on a round surface, we evaluate a new technique using an MFG for measuring isolated forearm rotation. Methods Patients with clinically healed distal radius fractures were enrolled in the study. Measurement of active forearm pronation and supination was recorded using 2 separate measurement techniques. These measurements were taken by 2 separate hand therapists with more than 10 years of clinical experience in a tertiary care setting at the beginning and end of hand therapy sessions for 3 consecutive weekly visits. Intraclass correlation coefficients (ICCs), standard error of measurement, and minimal detectable change were calculated for each technique. Results The point estimates for the MFG method demonstrated a slightly higher ICC than the standard method for pronation (0.86 vs 0.82). For supination, both measurement techniques displayed equally high pooled ICCs (0.95). The standard error of measurements for the MFG were 2.1 for pronation and 1.2 for supination compared with 2.9 (pronation) and 1.2 (supination) for the standard technique. These translate into 90% minimal detectable changes of 5° and 3° for the MFG pronation/supination compared with 7° (pronation) and 3° (supination) for the standard technique, respectively. Discussion Although the point estimates for the ICCs of the MFG method are equal or higher than the standard method, the confidence intervals for the ICCs overlap, indicating that the MFG is at least equivalent to the standard method in terms of inter-rater reliability. Level of evidence 2b.