Flexor Pronator Strain Clinical Pearls
Introduction
A flexor-pronator mass injury is a muscle tear or strain affecting the flexor-pronator muscles of the elbow joint. This injury is uncommon and primarily seen in athletes participating in throwing sports, though it can occasionally result from acute trauma like elbow dislocation.
Clinical Presentation and Diagnosis
Patients typically experience significant elbow pain, similar to ulnar collateral ligament (UCL) injury.
- history of throwing or racquet sports. It can also include repetitive gripping and/or elbow valgus stress activities.
- Symptoms include medial elbow pain distal to the medial epicondyle. This can occur during late cocking/early acceleration.
- Physical exam demonstrates medial elbow swelling and ecchymosis in acute strain. There can be tenderness distal to medial epicondyle.
- Provocative tests demonstrate pain with elbow extension and resisted wrist flexion or pronation. These patient can have a negative moving valgus stress test and normal neurovascular exam.
- Diagnosis is primarily clinical, with imaging used to rule out associated injuries like UCL damage.
Pathology and Imaging
The injury involves muscle tears, strains, or avulsions of the flexor-pronator group, usually distal to the medial epicondyle. It can be acute or chronic. Ultrasound may show hyper- or hypoechoic lesions within the muscle group, while MRI can grade the injury and differentiate it from medial epicondylitis. Indications for an MRI include: unclear source of medial elbow pain, grade severity of muscle strain or to rule out other causes of medial elbow pain such as UCL rupture.
Treatment and Prognosis
Conservative treatment is typically recommended, including:
- Pain control (NSAIDS, rest, physical therapy)
- Active rest
- Functional rehabilitation
- ROM and flexor pronator strengthening x 4-6 weeks
- outcomes typical resolution and return to sport in 4-6 weeks
A structured program helps athletes return to activity. Persistent or recurrent symptoms may indicate valgus instability.
Associated Conditions
Flexor-pronator mass injuries can be associated with:
- Valgus instability
- Elbow dislocation
- Medial epicondylitis
- Complications may include valgus instability, especially with continued valgus stress during throwing activities
