When to Order an X-ray for Joint Injuries
Use validated clinical decision rules—specifically the Ottawa Knee Rules, Pittsburgh Decision Rule for knees, and Ottawa Ankle Rules—to determine which patients require radiography; these rules achieve near-perfect sensitivity for detecting clinically significant fractures while reducing unnecessary imaging by 23-53%. 1
Clinical Decision Rules by Joint
Knee Injuries
Order knee radiographs if the patient meets ANY of the following Ottawa Knee Rule criteria: 1
- Age ≥55 years
- Palpable tenderness over the fibular head
- Isolated patellar tenderness (no other bony tenderness)
- Cannot flex knee to 90 degrees
- Cannot bear weight immediately after injury
- Cannot take 4 weight-bearing steps in the emergency department
Pittsburgh Decision Rule (alternative): Order radiographs if age <12 years OR >50 years, OR cannot take 4 weight-bearing steps 1
Special consideration: Children aged 5-12 years fall outside both rule ranges—consider radiographs despite lack of clinical symptoms 1
Ankle Injuries
Order ankle radiographs if the patient has:
- Point tenderness over the malleoli, talus, or calcaneus
- Inability to walk/bear weight 2
Do NOT order ankle radiographs if: No point tenderness over bony structures AND able to walk—the Ottawa Ankle Rules are negative 2
Hand and Wrist Injuries
Always obtain radiographs as initial imaging for suspected hand or wrist trauma 3
Minimum views required:
- Wrist: 3 views (PA, lateral, 45° semipronated oblique) 3
- Hand: 3 views (PA, lateral, oblique) 3
- Thumb: 2 views minimum (slight increase in yield with oblique) 3
Mandatory Exceptions—Always Order Radiographs
Clinical decision rules should NOT be applied when any of the following are present: 1
- Gross deformity
- Palpable mass
- Penetrating injury
- Prosthetic hardware present
- Multiple injuries making examination unreliable
- Altered mental status (head injury, intoxication, dementia)
- Neuropathy (paraplegia, diabetes, peripheral neuropathy)
- History suggesting increased fracture risk
Important caveat: Physician judgment supersedes clinical guidelines in all scenarios 1
Evidence Strength
The Ottawa rules demonstrate 100% sensitivity for detecting knee fractures and reduce unnecessary radiographs by 35% 1. The Pittsburgh rules are more specific but less extensively validated 4. Both are highly effective, though the Ottawa rules have NICE recommendation in the UK 4.
Common pitfall: The single most frequent error is ordering radiographs without performing proper physical examination first—86% of patients in one study received unnecessary radiographs due to inadequate screening 5. Always complete the clinical examination using these structured criteria before ordering imaging.
If Initial Radiographs Are Negative But Clinical Suspicion Remains High
Two options: