Valgus Stress Test of the Ulnar Collateral Ligament on Ultrasound in Throwers
Anatomy and Clinical Significance
The anterior band of the ulnar collateral ligament is the most clinically significant structure: it limits valgus stress on the elbow. The anterior band has a fan-shaped structure with a broad attachment to the medial epicondyle and a thin insertion on the sublime tubercle of the medial coronoid process of the ulna. The posterior band is a broad, thin ligament forming the floor of the cubital tunnel (according to Griffith, 2025).
Valgus Stress Test Technique
Dynamic assessment with valgus stress is performed with the elbow slightly flexed (at least 30°) to evaluate ligament damage (Jacobson, 2026). The maneuver can be performed with the patient lying supine with the arm extended: the edge of the examination table is used as a fulcrum on the humerus, and gravity creates the valgus load.
According to AIUM (2023), during the valgus stress test, the elbow may need to be flexed at various angles to move the olecranon out of the olecranon fossa. The assessment is conducted after examining the common flexor tendon and the anterior band of the ulnar collateral ligament.
Ultrasound Signs of Injury
| Type of Injury | Ultrasound Findings |
|---|---|
| Attenuated Ligament | In the longitudinal view, the ligament is thinned; under valgus stress, the ligament remains intact, but asymmetric widening of the joint space is observed |
| Full-Thickness Tear | Abnormal hypoechogenicity with no discernible fibers; widened medial joint space that increases with valgus stress |
The key quantitative indicator in dynamics is asymmetric widening of the medial joint space under load compared to the contralateral side. Specific threshold values for widening are not provided in the source fragments [to be clarified].
Application in Baseball Pitchers
Stress sonography is used to assess the risk of UCL injury in professional baseball pitchers based on ligament morphology and dynamic deviations; dynamic ultrasound of the anterior band of the UCL in asymptomatic pitchers is described (EFSUMB, 2022). The adequacy of ultrasound as the sole diagnostic method for medial UCL injuries is discussed (Park et al., 2020).
Frequently asked questions
At what angle should the elbow be flexed during the valgus stress test?
At least 30° (Jacobson, 2026). According to AIUM (2023), the angle may vary to move the olecranon out of the olecranon fossa.
Which portion of the UCL should be assessed first?
The anterior band, as it limits valgus stress and is the most clinically significant (Griffith, 2025).
How to create valgus load without an assistant?
The patient lies supine with the arm extended; the edge of the table serves as a fulcrum on the humerus, and valgus stress is created by gravity (Jacobson, 2026).
What sign indicates damage during dynamics?
Asymmetric widening of the medial joint space that increases with valgus stress; in full-thickness tears, hypoechogenicity with no discernible fibers (Jacobson, 2026).