Evaluation and Management of Anterior Forearm Pain with Erythema

Musculotendinous Injuries

The American College of Radiology recommends that distal biceps tendon tear be strongly considered when pain occurs during both pronation and supination because these motions stress the tendon at its radial tuberosity insertion. 1
Partial tears of the long‑head biceps tendon with an intact short head represent the most common injury pattern, whereas traumatic ruptures are more frequently associated with short‑head involvement. (Evidence based on imaging series) 2
Pain elicited by resisted elbow flexion is characteristic of distal biceps pathology, and accompanying anterior erythema may reflect an acute inflammatory response to the tendon injury. 3
An acute strain or tear of the flexor‑pronator mass originating from the medial epicondyle can produce anterior forearm pain during pronation and elbow flexion. 4

Medial collateral (ulnar) ligament injury of the elbow, typically following trauma, presents with pain on valgus stress and flexion. (Radiologic correlation) 2
Lateral collateral ligament complex injury may manifest as pain on external rotation of the forearm and joint instability. 4
Combined ligamentous injuries often accompany elbow dislocations and may involve both medial and lateral stabilizers. 1

The presence of erythema together with forearm pain mandates immediate evaluation for infection, including septic arthritis or deep soft‑tissue infection. (Clinical guideline) 5
Red‑flag symptoms such as fever, marked swelling, inability to move the joint, or systemic signs require urgent in‑person assessment to rule out osteomyelitis or septic arthritis. 5
Do not attribute erythema solely to inflammation; exclusion of infection is essential because delayed diagnosis of septic arthritis significantly increases morbidity. 5

Obtain a detailed mechanism of injury (e.g., direct trauma, fall on an outstretched hand, repetitive overhead activity, or insidious onset) to guide differential diagnosis. 5
Systematically assess for red‑flag features (fever, severe swelling, joint immobility, visible deformity, systemic illness) that necessitate urgent referral. 5
Localize tenderness: anterior cubital‑fossa tenderness is suggestive of distal biceps pathology, whereas proximal pronator‑teres tenderness points toward pronator syndrome. 3
Perform resisted supination (thumbs‑up position); pain indicates likely distal biceps tendon involvement. 1

Plain radiographs are the mandatory first‑line study to exclude fracture, dislocation, or avulsion injury of the elbow. (Radiology protocol) 6
When radiographs are normal or equivocal, MRI without contrast is the preferred advanced modality for evaluating suspected tendon, ligament, or muscle injuries. (Imaging guideline) 4
Ultrasound serves as an equivalent alternative to MRI for assessing distal biceps tendon tears and can detect fluid collections suggestive of infection. (Ultrasound guideline) 7
The flexion‑abduction‑supination (FABS) MRI view may provide additional diagnostic benefit in distinguishing high‑grade partial from complete distal biceps tendon tears. 1

Ultrasound demonstrates lower accuracy than MRI for detecting partial distal biceps tears (approximately 45 % vs. 86 % sensitivity); therefore, MRI is preferred when precise delineation is required for surgical planning. 3