In an older adult (>65 years) with sudden hip or groin pain after a fall, how can I differentiate a hip fracture from hip osteoarthritis regarding presentation, imaging findings, and initial management?

Differentiating Hip Fracture from Hip Osteoarthritis in Older Adults

In an older adult presenting with sudden hip or groin pain after a fall, suspect hip fracture first—this is a surgical emergency with significant mortality risk (8-10% at 30 days, 22-33% at 1 year), whereas hip osteoarthritis presents with chronic, progressive pain without acute trauma. 1

Clinical Presentation: Key Distinguishing Features

Hip Fracture (Post-Fall)

• Acute onset immediately following fall or trauma
• Unable to bear weight on affected leg 2
• Shortened, externally rotated leg on the affected side 3
• Pain is severe and constant, worsening with any movement
• Patient typically cannot ambulate at all 3
• Occurs in patients with mean age 77 years, often with osteoporosis 1

Hip Osteoarthritis (Chronic)

• Gradual onset over months to years, no acute trauma 4
• Pain exacerbated with activity, alleviated with rest 4
• Patient can typically ambulate with antalgic gait, often using assistive device 4
• Groin pain is most common location 5, 6
• Pain reproduced by passive internal rotation (sensitivity 66%, specificity 79%) 5
• Decreased passive hip adduction (sensitivity 80%, specificity 81%) or internal rotation measured by goniometer 5
• History often includes progressive functional decline over time 4

Critical Pitfall: Do not assume chronic hip pain rules out acute fracture—patients with pre-existing hip OA can sustain superimposed fractures 7.

Imaging Approach: Algorithmic Strategy

Initial Imaging for Suspected Hip Fracture

Step 1: Plain Radiography (ALWAYS first-line) 8, 9

• Obtain AP pelvis + cross-table lateral of symptomatic hip 8
• Detects 90% of hip fractures 8
• Also identifies concomitant pelvic fractures (sacrum, pubic rami) present in many patients 8
• Allows comparison to contralateral side 8

Step 2: If Radiographs Negative BUT Clinical Suspicion Remains High 8

• MRI pelvis and affected hip without contrast is the definitive next step 8
• MRI has near 100% sensitivity for occult hip fractures 8
• A negative MRI allows confident discharge from emergency department 8
• 39% of patients with negative radiographs but persistent clinical suspicion have surgical hip fractures on MRI 10
• Higher risk subgroups for occult fracture: age ≥80 years (44% occult fracture rate), equivocal radiographic report (58%), history of trauma (41%) 10

Step 3: Alternative if MRI Contraindicated

• CT pelvis and hips without contrast as problem-solving modality 8
• Less sensitive than MRI (79% vs 87% for bone scan) but acceptable alternative 10

Imaging for Suspected Hip Osteoarthritis

For chronic hip pain without trauma:

• AP pelvis + Lequesne's false profile lateral view 11
• Look for: joint space narrowing, osteophytes, subchondral sclerosis, cysts 11
• MRI is NOT routinely needed for OA diagnosis 11
• MRI only if considering alternative diagnoses (labral tear, avascular necrosis, stress fracture) 6, 12

Important Caveat: Radiographic OA changes correlate poorly with symptoms—many asymptomatic patients have radiographic OA 11. Clinical correlation is essential.

Initial Management: Time-Critical Differences

Hip Fracture Management

• Surgery within 24-48 hours of hospital admission (moderate strength recommendation) 1
• Delays beyond 12 hours increase 30-day mortality 9
• Immediate pain control: opioids with caution (40% have renal dysfunction), consider femoral/fascia iliaca nerve blocks 3
• VTE prophylaxis (preferably low-molecular-weight heparin) 3, 7
• Prophylactic antibiotics against Staphylococcus aureus before surgery 2
• Mortality in first year is three times higher than general geriatric population 1

Hip Osteoarthritis Management

• NSAIDs when not contraindicated (strong strength recommendation) 4
• Acetaminophen may be considered (consensus option) 4
• Physical therapy for mild-to-moderate symptoms (moderate strength recommendation) 4
• Weight-bearing as tolerated—no surgical urgency 4
• Consider total hip arthroplasty for end-stage disease refractory to conservative measures 4

Red Flags Requiring Immediate Action

Obtain imaging SAME DAY if:

• Acute hip/groin pain after fall with inability to bear weight
• Shortened, externally rotated leg
• Severe pain with any hip movement
• Patient cannot ambulate

Do NOT delay imaging for "trial of conservative management" in post-fall patients—this increases morbidity and mortality 9.

Common Clinical Pitfalls

1. Assuming normal radiographs exclude fracture: 10% of hip fractures are radiographically occult—proceed to MRI if clinical suspicion persists 8

2. Mistaking isolated greater trochanter fracture for benign finding: 92% of patients with isolated GT fracture on radiograph have surgical hip fractures on MRI 10

3. Delaying surgery for "medical optimization": Surgery should occur within 24-48 hours unless patient has acute, reversible medical conditions 1

4. Ordering MRI first-line: Always start with plain radiographs—they detect 90% of fractures and are faster, cheaper, and more accessible 8, 9

5. Assuming chronic hip pain means OA, not fracture: Patients with pre-existing OA can sustain acute fractures—the acute change in symptoms and mechanism of injury are key differentiators 7