Updated: 6/24/2017

Flexor Pronator Strain

Review Topic
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  • Acute or chronic muscle strain of the flexor pronator mass, distal to its origin on the medial epicondyle
  • Epidemiology
    • demographics
      • golfers
      • cricket players
      • throwing athletes
  • Pathophysiology
    • acute muscle tear
      • single event of a large, eccentric force during resisted wrist flexion, forearm pronation, and valgus at the elbow
        • chronic overuse can lead to acute flexor pronator rupture
      • sudden onset of pain and flexor weakness
    • chronic tendonitis
      • repetitive elbow valgus, wrist flexion, and forearm pronation
  • Associated conditions
    • ulnar collateral ligament insufficiency 
      • should be ruled out in throwing athletes
  • Prognosis
    • typically resolves with 4-6 weeks of activity restriction
  • Flexor pronator mass provides dynamic support to the medial elbow against valgus stress
  • Flexor pronator mass includes (proximal to distal) 
    • Pronator Teres (median n.)  
    • Flexor Carpi Radialis (median n.)  
    • Palmaris Longus (median n.) 
    • FDS (median n.)   
    • Flexor Carpi Ulnaris (ulnar n.) 
  • History
    • acute event of hitting the ground during golf, bat, or racquet swing
    • history of throwing or racquet sports
    • repetitive gripping and/or elbow valgus stress activities
  • Symptoms
    • pain
      • medial elbow pain distal to the medial epicondyle
      • chronic pain during late cocking/early acceleration
  • Physical exam
    • medial elbow swelling and ecchymosis in acute strain
    • tenderness distal to medial epicondyle
    • provocative tests
      • pain with elbow extension and resisted wrist flexion or pronation
    • examine for associated conditions
      • negative moving valgus stress test
      • normal neurovascular exam
  • Radiographs
    • usually normal
  • MRI 
    • indications
      • unclear source of medial elbow pain
      • grade severity of muscle strain
      • rule out other causes of medial elbow pain such as UCL rupture
    • findings  
      • edema in flexor pronator mass
      • partial tearing or complete rupture of flexor pronator mass
  • Medial epicondylitis 
  • UCL injury 
  • Valgus extension overload with posteromedial olecranon impingement 
  • Nonoperative
    • NSAIDS, rest, physical therapy, steroid injections
      • indications
        • first line of treatment 
      • technique
        • ROM and flexor pronator strengthening x 4-6 weeks
        • corticosteroid injection for chronic flexor pronator tendonitis
          • rarely needed
          • avoid UCL due to risk of rupture
      • outcomes
        • typical resolution and return to sport in 4-6 weeks
  • Operative
    • primary surgical repair
      • indications
        • significant (>2.5 cm) retraction 
  • Continued medial elbow pain and valgus instability
    • unrecognized UCL insufficiency

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