The ulnar collateral ligament of the elbow is often injured by repetitive stress from overhead motions such as throwing. This commonly occurs in athletes who play sports, such as baseball in this case. 

In addition to UCL injuries, ulnar neuritis and medial epicondylitis may also occur. Under the guidance of a skilled operator, ultrasound is a convenient, reliable modality with the capability of providing a real-time diagnosis of these injuries (and many others) at the onset of symptoms or after the injury. Performing stress maneuvers during dynamic imaging of the elbow can assess instability of the elbow and the extent of injury.

In this example, the patient presents with tenderness over the medial epicondyle. Full range of motion of the elbow. No ulnar nerve subluxation present. 

Grayscale, power doppler, and dynamic ultrasound of the left elbow were performed using a high frequency 18 MHz linear transducer. 

The following structures were evaluated in the medial compartment of the elbow:

• Ulnar Collateral Ligament
• Humeroulnar Joint 
• Common Flexor Tendon
• Ulnar Nerve 

Ulnar Collateral Ligament Tear

Thickened UCL with a partial-thickness tear involving the superficial fibers of the ligament at the medial epicondyle attachment. 

UCL with mild hyperemia present

Dynamic Ultrasound of UCL

There is slight widening of the joint space with valgus stress.

Medial Epicondylitis

Small low-grade interstitial tear of the common flexor tendon involving less than 25% thickness of the thickened tendon fibers.

Ulnar Neuritis

There is enlargement and fascicular swelling of the ulnar nerve within the cubital tunnel. No space occupying lesion or triceps hypertrophy present.

Cross-sectional area (CSA) measurement of the Ulnar Nerve shows significant enlargement within the cubital tunnel. 

Tracing the nerve inside the hyperechoic epineurium layer at the point of maximal enlargement is the most appropriate measurement in evaluating entrapment neuropathy. The mean value of the ulnar nerve at the level of the medial epicondyle is 0.066 cm squared. 

Impression:

UCL tear. Joint spaces are preserved. Medial epicondylitis. Small low-grade interstitial tear of Common flexor tendon. Surrounding soft tissue edema.