Increased palpation tenderness and muscle strength deficit in the prediction of tendon hypertrophy in symptomatic unilateral shoulder tendinopathy: an ultrasonographic study

ObjectiveIn asymptomatic, normal tendons, the difference in tendon thickness between sides is less than 15%. In this study, three tests were used to examine differences between symptomatic and asymptomatic shoulders.DesignCross-sectional study. The three tests were performed in sequence. The observer was blinded in the maximal pain-free isometric force test.SettingOutpatient physiotherapy clinic at Bergen University College, Norway.ParticipantsSixty-four patients with an exclusive, tentative diagnosis of unilateral shoulder tendinopathy.Main outcome measuresDifferences in maximal pain-free isometric force, tendon pain pressure and tendon thickness measured by ultrasonography.ResultsThis paper follows the STARD recommendations for papers on diagnostic accuracy. When cut-off values for within-subject side differences were selected at ≥0.8 mm for tendon thickness (TTdiff), ≥10 N for maximal pain-free isometric force (PFFdiff) and ≥0.6 kg for tendon pain pressure (PPTdiff), positive tests were found in 92% of patients. All three tests were sensitive for the detection of within-subject side differences with the selected cut-off values (TTdiff, n = 60/64; PPTdiff, n = 59/64; PFFdiff, n = 57/64; P > 0.35). There were strong agreements between the three tests: TTdiff and PFFdiff, 0.89; TTdiff and PPTdiff, 0.83; and PFFdiff and PPTdiff, 0.84. When both clinical tests were positive (PFFdiff and PPTdiff), the positive predictive value was excellent (94%) for finding increased tendon thickness in the symptomatic side on ultrasonography.ConclusionsWithin the limitations of this partially blinded study, patients with unilateral shoulder tendinopathy exhibited significant differences between sides in all three tests. The combination of the two clinical tests seems to be valid for the detection of unilateral shoulder tendinopathy if other diagnoses have been excluded.