AimTo evaluate the inter-rater reliability of measuring structural changes in the tendon of patients, clinically diagnosed with supraspinatus tendinopathy (cases) and healthy participants (controls), on ultrasound (US) images captured by standardised procedures.MethodsA total of 40 participants (24 patients) were included for assessing inter-rater reliability of measurements of fibrillar disruption, neovascularity, as well as the number and total length of calcifications and tendon thickness. Linear weighted κ, intraclass correlation (ICC), SEM, limits of agreement (LOA) and minimal detectable change (MDC) were used to evaluate reliability.Results‘Moderate—almost perfect’ κ was found for grading fibrillar disruption, neovascularity and number of calcifications (k 0.60–0.96). For total length of calcifications and tendon thickness, ICC was ‘excellent’ (0.85–0.90), with SEM(Agreement) ranging from 0.63 to 2.94 mm and MDC(group) ranging from 0.28 to 1.29 mm. In general, SEM, LOA and MDC showed larger variation for calcifications than for tendon thickness.ConclusionsInter-rater reliability was moderate to almost perfect when a standardised procedure was applied for measuring structural changes on captured US images and movie sequences of relevance for patients with supraspinatus tendinopathy. Future studies should test intra-rater and inter-rater reliability of the method in vivo for use in clinical practice, in addition to validation against a gold standard, such as MRI.Trial registration numberNCT01984203; Pre-results.