What should be ordered to prevent further knee injury in a patient who repeatedly bumps his knee?

Order Knee Radiographs (X-rays) to Assess for Fracture or Underlying Injury

If the patient has focal tenderness, effusion, or inability to bear weight from repeatedly bumping the knee, order anteroposterior (AP) and lateral knee radiographs immediately to rule out fracture. 1

Clinical Decision-Making Algorithm

Step 1: Apply Ottawa Knee Rule Criteria

Order radiographs if ANY of the following are present:

• Age ≥55 years (or ≥50 years per Pittsburgh Rule)
• Inability to bear weight (cannot take 4 weight-bearing steps)
• Isolated patellar tenderness (no other bony tenderness)
• Bony tenderness at head of fibula
• Inability to flex knee to 90 degrees

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Step 2: Consider Special Circumstances

Override clinical decision rules and obtain radiographs if the patient has:

• Altered mental status (dementia, intoxication)
• Neuropathy (diabetes, paraplegia)
• Multiple injuries making exam unreliable
• Gross deformity or palpable mass
• Prosthetic hardware

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Step 3: Imaging Protocol

When radiographs are indicated, obtain minimum two views:

• Anteroposterior (AP) view
• Lateral view (knee at 25-30° flexion)
• Consider patellofemoral view if patellar injury suspected

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Prevention Strategy After Imaging

If Radiographs Are Normal:

Prescribe a knee brace or immobilizer for protection during activities to prevent further trauma while the patient modifies behavior or environment. 2

If Radiographs Show Injury:

• Fracture detected: Orthopedic referral, immobilization
• No fracture but persistent symptoms: Consider MRI for occult fracture or internal derangement 1

Important Caveats

The Ottawa Knee Rule reduces unnecessary radiographs by 53% while maintaining near 100% sensitivity for fractures. 1 However, physician judgment supersedes clinical guidelines in all scenarios. 1

Repeated minor trauma can cause occult fractures not visible on initial radiographs. If pain persists despite normal X-rays, CT may detect radiographically occult fractures with 100% sensitivity (versus 83% for plain films). 1

For long-term prevention, address the underlying cause of repeated bumping:

• Evaluate for proprioceptive deficits or neuropathy 1
• Consider gait analysis if falls are frequent
• Environmental modifications (remove obstacles, improve lighting)
• Protective knee padding or bracing during high-risk activities 2