What is the initial workup for a patient with a swollen and tender ankle at urgent care?

Initial Workup for Swollen and Tender Ankle at Urgent Care

Apply the Ottawa Ankle Rules immediately to determine if radiography is needed—this is the validated, evidence-based first step for any patient presenting with ankle trauma. 1

Clinical Assessment Framework

History Taking: Establish Mechanism of Injury

• Determine if trauma occurred: Ask specifically about inversion injury, fall, twisting mechanism, or any precipitating event 2
• If NO trauma history exists: This fundamentally changes your diagnostic approach—you must rule out septic arthritis, inflammatory arthropathy (gout, pseudogout, rheumatoid arthritis), and deep vein thrombosis rather than applying standard sprain protocols 2
• Assess weight-bearing ability: Document if the patient could bear weight immediately after injury and whether they can take 4 steps in the urgent care setting 1
• Timeline matters: Note if pain has persisted >1 week but <3 weeks, as this affects imaging decisions 1

Physical Examination: Systematic Palpation and Testing

• Point tenderness assessment: Palpate the medial malleolus, posterior edge and inferior tip of the lateral malleolus, talus, and calcaneus—tenderness at any of these sites is a positive Ottawa Ankle Rule 1
• Include the base of the fifth metatarsal: Palpate distal to the tuberosity, as this must be evaluated as part of ankle trauma assessment 1
• Vascular examination: Palpate pedal pulses and assess for any signs of peripheral arterial disease, particularly in diabetic or older patients 1
• Inspect for deformity, swelling distribution, hematoma, and skin integrity 3, 4
• Avoid manipulating the ankle prior to radiographs unless there is neurovascular deficit or critical skin injury, as this may cause complications 1

Imaging Decision Algorithm

If Ottawa Ankle Rules are POSITIVE (any of the following):

1. Inability to bear weight immediately after injury, OR
2. Point tenderness over medial malleolus, posterior edge/inferior tip of lateral malleolus, talus, or calcaneus, OR
3. Inability to ambulate 4 steps in urgent care

Then order three-view radiography (anteroposterior, lateral, and mortise views) including the base of the fifth metatarsal 1, 3

• The Ottawa Ankle Rules demonstrate 92-99% sensitivity for detecting ankle fractures 1
• Weight-bearing radiographs provide superior information about fracture stability if the patient can tolerate them—a medial clear space <4 mm confirms stability 1
• Do NOT order CT, MRI, bone scan, or ultrasound as first-line imaging when Ottawa Ankle Rules are positive 1

If Ottawa Ankle Rules are NEGATIVE:

No imaging is routinely indicated 1

• Radiography, CT, MRI, bone scan, and ultrasound are not routinely indicated for acute ankle trauma when Ottawa Ankle Rules are negative 1
• Consider clinical follow-up if symptoms persist beyond expected timeframe 3

Critical Exclusionary Criteria (Ottawa Ankle Rules DO NOT Apply)

Do not use Ottawa Ankle Rules if any of the following are present 1:

• Age <5 years
• Intoxication
• Distracting painful injuries
• Diminished sensation in legs (peripheral neuropathy)
• Gross swelling preventing palpation of malleolar bone tenderness
• Pregnancy

In these patients, proceed directly to radiography regardless of clinical findings 1

Special Clinical Scenarios Requiring Modified Approach

Atraumatic Ankle Swelling (No Injury History)

This is NOT an ankle sprain and requires a completely different workup 2:

• Rule out septic arthritis first: Can present with isolated joint swelling and tenderness even without fever or erythema 2
• Consider inflammatory arthropathy: Gout, pseudogout, or rheumatoid arthritis commonly present with atraumatic joint swelling in middle-aged adults 2
• Assess for deep vein thrombosis: Unilateral ankle swelling without trauma warrants venous pathology evaluation 2
• Do NOT apply RICE protocols or standard sprain management without establishing traumatic mechanism—this delays diagnosis of serious conditions 2

Diabetic Patients with Neuropathy

• Cannot use Ottawa Ankle Rules due to diminished sensation 1
• Proceed directly to radiography for any ankle complaint 1
• Assess for Charcot neuroarthropathy if bilateral warmth present—temperature difference ≥2°C between feet suggests active disease 5
• Perform comprehensive vascular assessment including pedal pulses 1

Laboratory Testing Considerations

Laboratory tests are NOT routinely part of initial ankle trauma workup unless specific clinical features suggest:

• Septic arthritis (joint aspiration if high suspicion) 2
• Inflammatory arthropathy (uric acid, inflammatory markers if atraumatic presentation) 2
• Bilateral swelling suggesting systemic disease (urinalysis with protein quantification, renal function) 5

Common Pitfalls to Avoid

• Do not order foot radiographs routinely with ankle radiographs—in the presence of inversion injury or ankle fracture, foot radiographs have low yield except for the fifth metatarsal base 1
• Do not order knee radiographs with ankle trauma—these have extremely low yield 1
• Do not miss snowboarder's fracture (lateral talar process)—look specifically for swelling inferior to lateral malleolus and the "V sign" on radiographs, as these are overlooked 40-50% of the time 1
• Do not assume all ankle swelling is traumatic—absence of injury mechanism requires completely different diagnostic approach 2

Disposition and Follow-up

• If radiographs show fracture: Refer to orthopedics based on fracture type and stability 1
• If radiographs negative but high clinical suspicion persists: Consider MRI or CT for occult fractures or ligamentous injury at follow-up (not in urgent care setting) 1, 3
• Optimal timing for ligamentous injury assessment is 4-5 days post-injury when swelling has decreased 3
• If atraumatic presentation: Urgent medical evaluation needed if inability to bear weight develops, systemic symptoms emerge, rapid progression occurs, or erythema suggesting infection appears 2