Initial Management of Acute Knee Injury After Fall
Obtain knee radiographs immediately as the first diagnostic step, since this patient has focal pain (below the patella and posteriorly) 24 hours after a fall, which meets criteria for mandatory imaging. 1
Imaging Algorithm
Step 1: Plain Radiographs (Required)
- Knee radiographs are the mandatory initial imaging study when any of the following are present after a fall: focal tenderness, effusion, or inability to bear weight 1
- This patient has focal tenderness in two locations (infrapatellar and posterior knee), which automatically triggers the need for radiographs regardless of age or ability to walk 1
- The Ottawa Knee Rule and Pittsburgh Decision Rule both support radiography when focal tenderness is present 1
Step 2: Advanced Imaging (If Radiographs Negative)
- If radiographs show no fracture but pain persists, proceed to MRI knee without IV contrast to evaluate for occult fractures, meniscal tears, ligament injuries, or internal derangement 1
- MRI is the appropriate next step for adults when radiographs are negative but clinical suspicion remains high 1
Pain Management Protocol
First-Line Therapy
- Start oral or topical NSAIDs immediately for pain control and anti-inflammatory effect 2, 3, 4
- NSAIDs combined with acetaminophen (500 mg acetaminophen + 200 mg ibuprofen) provide superior analgesia compared to opioid regimens and should be the foundation of pain management 4
- Topical NSAIDs are specifically recommended for non-low back musculoskeletal injuries like knee trauma 3
Adjunctive Measures
- Apply ice through a wet towel for 10-minute periods for acute pain relief 5
- Ice therapy provides short-term symptom relief without affecting long-term outcomes 5, 2
Critical Medication Safety Points
- Use lower acetaminophen doses if the patient has hepatic disease, malnutrition, or alcohol use disorder 3
- Use NSAIDs cautiously if the patient has history of gastrointestinal bleeding, cardiovascular disease, or chronic kidney disease 3, 6
- Reserve opioids only for severe or refractory pain that does not respond to NSAID/acetaminophen combination 3, 4
Activity Modification
- Implement relative rest from activities that reproduce pain (such as jumping, squatting, or prolonged standing) 5
- Avoid complete immobilization or casting, as this causes muscular atrophy and deconditioning 5
- Maintain activities that do not reproduce pain to prevent deconditioning 5
Red Flags Requiring Urgent Evaluation
Vascular Emergency Indicators
- If there is gross deformity, suspected knee dislocation, or signs of vascular compromise (absent pulses, cool extremity), obtain CTA of the lower extremity immediately in addition to radiographs 1
- Popliteal artery injuries occur in approximately 30% of posterior knee dislocations and require prompt surgical intervention 1
Infection Concerns
- If there is concern for septic arthritis (fever, severe swelling, inability to move joint), perform aspiration for synovial fluid analysis before initiating any treatment 2
- Never inject corticosteroids if infection has not been excluded, as this can worsen septic arthritis 2
Common Pitfalls to Avoid
- Do not skip radiographs even if the patient can walk—focal tenderness mandates imaging 1
- Do not inject corticosteroids into or near the patellar tendon, as this inhibits healing and predisposes to spontaneous rupture 5
- Do not perform aspiration for routine traumatic effusions without specific indication (suspected infection, crystal arthropathy, or tense effusion causing significant limitation), as fluid will reaccumulate 2
- Do not prescribe opioids as first-line therapy—multimodal nonopioid analgesia is more effective and safer 3, 4
Expected Timeline
- Most patients with acute knee injuries respond to conservative management within weeks to months when appropriately treated 2
- Re-evaluate within 48-72 hours if pain is not improving with initial management 3
- If radiographs are negative but symptoms persist beyond 1-2 weeks, proceed to MRI evaluation 1