Pathological Classification of Lateral Elbow Tendinopathy Based on Fiber Orientation, Blood Flow Velocity of Radial Recurrent Artery, and Patient-Reported Outcome Measures

Background/Objectives: This study aimed to establish a method for evaluating the pathology of lateral elbow tendinopathy (LET) using ultrasonography. Methods: The LET group consisted of 47 patients with 50 elbows, and the control group consisted of 50 healthy adults with 50 elbows. The variables used for the pathological classification of LET included the peak systolic velocity (PSV) of the radial recurrent artery (RRA), fiber orientation intensity, numeric rating scale (NRS), Disabilities of the Arm, Shoulder, and Hand (DASH) score, and duration of symptoms. Classification was performed using principal component and cluster analyses. Results: The PSV of the RRA was significantly higher in the LET group (19.10 ± 4.63 cm/s) than in the control group (16.04 ± 2.96 cm/s). The fiber orientation intensity was significantly lower in the LET group (1.62 ± 0.15) than in the control group (1.73 ± 0.12). LET can be classified into three clusters. Cluster 1 showed decreased fiber orientation and moderate NRS and DASH scores. Cluster 2 demonstrated increased PSV of the RRA and severe NRS and DASH scores. Cluster 3 maintained a normal PSV of the RRA and fiber orientation, with mild NRS and DASH scores. No statistically significant differences were noted in the duration of symptoms between clusters. However, symptom duration tended to be longer in Clusters 1, 2, and 3. Conclusions: This study suggests that LET can be classified into mild, inflammatory, and degenerative phases.