Image Interpretation: Focal hypoechogenicity and disruption of the normal fibrillar echotexture at the proximal attachment of the UCL anterior bundle, consistent with a partial tear of the proximal-to-midsubstance region. No complete discontinuity of ligamentous fibers is seen. A PRP injection procedure is visualized, with the needle identified in long axis advancing to the tear site under real-time ultrasound guidance. Findings correlate with the patients clinical presentation and were confirmed on MR arthrography. Repeat ultrasonography at approximately 4 months post-PRP demonstrates interval improvement in fibrillar echotechture with decreased conspicuity of the prior defect of the UCL anterior bundle, correlating with the patient’s clinical recovery and return to prior level of play.

Teaching Pearl: Ultrasound is well-suited for serial follow-up imaging after PRP injection. In this case, ultrasound at 4 months post-injection demonstrated sonographic improvement, paralleling the patient’s clinical recovery and return to play. Compared with repeat MRI, ultrasound offers low cost, point-of-care availability, and the ability to perform dynamic stress assessment in the same encounter, making it a practical first-line modality for monitoring structural healing after orthobiologic intervention. PRP can produce structural ligamentous reconstitution even in the subacute or chronic setting. This case provides proof-of-concept support for PRP injection as a viable nonoperative option for recreational overhead athletes with partial proximal UCL tears. After failing structured physical therapy and equipment modification, the patient received PRP approximately 9 months after injury onset. At 4-month follow-up, ultrasound demonstrated reconstitution of the UCL with restored fibrillar echotexture and resolution of the previously visualized partial tear, and the patient had returned to his prior level of play. Notably, this case demonstrates that PRP can drive structural healing on imaging, not merely clinical improvement, even when administered well after the acute injury window and after failed conservative management. This raises the question of whether earlier PRP intervention, prior to scar tissue formation, may yield even more robust outcomes by facilitating true ligamentous reconstitution rather than fibrous repair. Regardless, this case supports PRP as a viable option even in the subacute or chronic setting, with documented structural and clinical recovery. Conventional MRI has significant limitations in UCL evaluation and may have limited sensitivity for partial UCL injuries. Standard coronal sequences are frequently non-diagnostic due to magic angle artifact, suboptimal elbow positioning, and the oblique course of the UCL anterior bundle relative to conventional imaging planes. The FEVER view MRI, which positions the elbow in flexion with valgus stress and external rotation, optimizes ligament orientation and substantially improves sensitivity for UCL tears. When clinical suspicion is high and standard MRI is negative, clinicians should pursue FEVER view MRI and/or dynamic stress ultrasound before concluding the UCL is intact. Dynamic stress ultrasound may offer complementary diagnostic value to conventional MRI in the evaluation of UCL tears. Systematic review data suggest dynamic stress ultrasound can achieve sensitivity of approximately 96% for UCL tears, while the reported sensitivity of conventional (non-contrast) MRI ranges widely from 57–100% depending on study population and technique, a variability that may partly explain why UCL pathology is occasionally identified on ultrasound despite a negative standard MRI. One proposed advantage of dynamic stress ultrasound is its functional capability: applying valgus stress during imaging may reveal ulnohumeral joint gapping even when the ligament appears morphologically intact or only subtly abnormal on static imaging. A side-to-side stress delta of >1 mm has been cited as a threshold for UCL insufficiency in some studies. MR arthrography generally demonstrates higher sensitivity than conventional MRI (81–100%), and one study of baseball players found that combining stress ultrasound with MRA raised diagnostic accuracy to 98% compared to either modality alone (88% for MRA, 87% for stress US), suggesting these approaches may be complementary rather than competing. Current ACSM guidelines describe dynamic ultrasound as “an increasingly used modality” for UCL evaluation, and the ACR Appropriateness Criteria acknowledge its utility while noting that more rigorous comparative studies are still needed, particularly in the acute setting. Campbell RE, McGhee AN, Freedman KB, Tjoumakaris FP. Diagnostic Imaging of Ulnar Collateral Ligament Injury: A Systematic Review. Am J Sports Med. 2020;48(10):2568–2576. Chen KC, Ha AS, Bartolotta RJ, et al. ACR Appropriateness Criteria® Acute Elbow and Forearm Pain. J Am Coll Radiol. 2024. Roedl JB, Gonzalez FM, Zoga AC, et al. Potential Utility of a Combined Approach With US and MR Arthrography to Image Medial Elbow Pain in Baseball Players. Radiology. 2016;279(3):827–837. Herring SA, Kibler WB, Putukian M, et al. Initial Assessment and Management of Select Musculoskeletal Injuries: A Team Physician Consensus Statement. Med Sci Sports Exerc. 2024.