What is the difference between a shoulder contusion and a shoulder strain?

Main Difference Between Shoulder Contusion and Shoulder Strain

A shoulder contusion is an injury to soft tissues caused by direct trauma resulting in bruising, while a shoulder strain involves stretching or tearing of muscles or tendons due to overexertion or overstretching.

Shoulder Contusion

Definition and Mechanism

• Results from direct blunt trauma or impact to the shoulder area 1
• Common in contact sports like football and rugby 2, 3
• Caused by a direct blow in approximately 70% of cases 3

Characteristics

• Involves bruising of soft tissues including muscle, periosteum, and potentially bone
• MRI findings typically show:
  • Peritendon edema at the myotendinous junction
  • Critical zone tendon edema
  • Subentheseal bone bruises 3
• May present with bone marrow contusion visible on MRI 1

Clinical Presentation

• Localized pain and tenderness at the site of impact
• Visible bruising may develop
• Limited range of motion due to pain
• Rotator cuff contusions account for nearly half of all shoulder injuries in professional football players 3

Shoulder Strain

Definition and Mechanism

• Involves stretching or tearing of muscles or tendons 4
• Usually results from:
  • Overexertion
  • Overstretching
  • Excessive force during movement
  • Repetitive motions

Characteristics

• Affects the musculotendinous unit (where muscle connects to tendon)
• Can range from mild (Grade I) to complete tears (Grade III)
• Often involves the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis)
• No bone marrow involvement unless there's an associated injury

Clinical Presentation

• Pain that worsens with specific movements
• Weakness in the affected muscle group
• Limited range of motion due to pain and weakness
• May develop gradually or suddenly depending on mechanism

Key Diagnostic Differences

Imaging Findings

• Contusion: MRI shows soft tissue edema, potential bone bruising, and intact muscle/tendon fibers 1, 3
• Strain: MRI shows disruption of muscle or tendon fibers, ranging from minimal (Grade I) to complete tears (Grade III) 1

Physical Examination

• Contusion: Tenderness directly over the site of impact, pain with direct pressure
• Strain: Pain with active contraction of the affected muscle, potential weakness with specific movements

Treatment Approaches

• Contusion: Most respond to conservative treatment with modalities and rehabilitation; only about 11% may require surgical intervention 3
• Strain: Treatment depends on severity - conservative management for mild to moderate strains, possible surgical intervention for complete tears 4

Clinical Implications

When evaluating shoulder injuries, distinguishing between contusion and strain is important for proper treatment planning:

1. Mechanism of injury provides the most important initial clue:

   • Direct blow suggests contusion
   • Overexertion or sudden movement suggests strain

2. MRI is the preferred imaging modality for both conditions, as it can:

   • Detect bone marrow contusion
   • Assess soft tissue damage
   • Evaluate the integrity of the rotator cuff 1

3. Treatment approach may differ:

   • Contusions typically heal with rest and conservative management
   • Strains may require more targeted rehabilitation or surgical intervention depending on severity

Remember that these injuries can coexist, particularly in high-impact trauma situations where both direct contusion and overstretching of tissues may occur simultaneously.