Purpose/Aim: This study investigated the reliability and validity of shoulder strength measurements using a digital force gauge and strain gauge in diabetic frozen shoulder patients. Materials/Methods: Digital force gauge and strain gauge to measure shoulder flexion, abduction, internal and external rotation in diabetic frozen shoulder patients. Results: Excellent intrarater reliability was present with Intraclass Correlation Coefficients (ICC- 3,k) for Force Gauge ≥ 0.95. The concurrent validity Force Gauge was good with ICC (3,k) values of ≥ 0.85. The 95% limits of agreement suggest that the Force Gauge measurement instruments can be expected to strength from 2° to 20°. Digital force gauge flexion, abduction, external rotation and internal rotation measurements had a greater mean and standard deviation than strain gauge flexion, abduction, external rotation and internal rotation measurements. Conclusions: This investigation is the first of its kind to evaluate the reliability and concurrent validity of strain gauge and force gauge measurements of muscles strength of shoulder flexion, abduction, external and internal rotation. When used with the measurement procedures outlined in this investigation, both techniques are reliable, as evidenced by reliability coefficients that exceed 0.90 (the threshold recommended for making clinical decisions). Good concurrent validity statistics were produced; however, one should recognize the potential ranges of disagreement between the two measurement instruments used in this study. When monitoring or comparing static shoulder strength measurements both researchers and clinicians should consider using similar instruments.