How are acute patellar dislocations evaluated and managed in the emergency department, including neurovascular assessment, reduction technique, immobilization, imaging, and follow‑up?

Acute Patellar Dislocation Management

Initial Assessment and Reduction

For acute patellar dislocations, immediately assess neurovascular status, perform reduction if still dislocated, provide analgesia with NSAIDs or opioids for severe pain, and obtain radiographs before and after reduction to rule out fractures. 1

Neurovascular Examination

• Check for intact pulses, capillary refill, and sensation in the affected extremity 2
• Test peroneal and tibial nerve function, as nerve injuries can cause significant long-term morbidity 2
• Document any vascular compromise immediately, as this would indicate a more severe injury pattern 2

Reduction Technique

• Most patellar dislocations reduce spontaneously before arrival to the emergency department 3
• If still dislocated, perform closed reduction by extending the knee while applying gentle medial pressure on the lateral patella 3
• For rare superior-lateral dislocations with vertical axis rotation, use hip flexion, modified varus-valgus force, and knee extension 4
• Consider early orthopedic consultation for complex dislocations that fail traditional reduction attempts 4

Pain Management

Administer NSAIDs as first-line analgesia for acute patellar dislocation, escalating to opioids if pain is severe enough to cause vomiting or other systemic symptoms. 1

• Apply ice therapy immediately using melting ice water through a wet towel for 10-minute periods 1
• NSAIDs provide effective short-term pain relief for acute ligamentous injuries 1
• Severe pain with vomiting warrants opioid analgesia and raises concern for displaced osteochondral fragments requiring surgical intervention 1

Imaging Protocol

Obtain anteroposterior, lateral, and patellofemoral (axial) radiographs as the initial imaging study for all first-time patellar dislocations. 5, 1, 6

Mandatory Radiographic Views

• Minimum two views: anteroposterior and lateral (knee flexed 25-30 degrees) 5
• Add patellofemoral (axial) view to evaluate for patellar fractures, subluxation degree, and confirm reduction 5, 1, 6
• Cross-table lateral view with horizontal beam can visualize lipohemarthrosis, indicating intra-articular fracture 5

Advanced Imaging Indications

Follow initial radiographs with MRI to characterize bone and soft-tissue injuries, particularly osteochondral fractures, bone marrow contusions, and medial patellofemoral ligament (MPFL) injury. 5, 1, 6

• MRI aids in diagnosis and characterization of injuries associated with transient lateral patellar dislocation 5, 6
• MRI is essential for risk stratification and identifying patients at high risk for recurrence 7
• CT is not routinely indicated unless complex fractures need better characterization 5
• Ultrasound, bone scan, and MR arthrography are not appropriate for initial evaluation 5

Immobilization and Functional Support

Use functional support with an ankle-style functional brace for 4-6 weeks rather than rigid immobilization, which should be limited to a maximum of 10 days if used at all for severe pain or edema. 1, 6

• Functional braces show the greatest treatment effects compared to other support types 6
• Rigid immobilization beyond 10 days increases stiffness and impairs mobility 1
• Transition from any initial immobilization to functional support as soon as pain and edema allow 1, 6

Treatment Algorithm Based on Imaging Findings

Nonoperative Management (First-Line)

Approximately 60-70% of patients with first-time traumatic patellar dislocation respond well to nonoperative treatment consisting of functional bracing followed by rehabilitation. 1, 6, 3, 8

• Conservative management is the treatment of choice for uncomplicated first-time dislocations 3, 8
• Functional support for 4-6 weeks followed by progressive rehabilitation 1, 6
• Redislocation rate is approximately 26% even with appropriate treatment 8
• Good to excellent functional results occur in 85% of patients at long-term follow-up 8

Surgical Indications

Surgery is indicated for osteochondral fractures with loose bodies, substantial disruption of medial patellar stabilizers, laterally subluxated patella with normal contralateral alignment, or failure to improve with appropriate rehabilitation. 1, 7, 3

• Osteochondral fragments require fixation plus soft tissue stabilization 7, 3
• Major defects of the parapatellar ligament complex warrant surgical repair 3, 8
• High-risk patients (younger age, skeletal immaturity, contralateral instability, trochlear dysplasia, patella alta, increased tibial tubercle-trochlear groove distance) may benefit from early soft tissue stabilization 7
• Arthroscopy reveals significant osteochondral defects not visible on radiographs in 40% of cases 9

Follow-Up and Risk Stratification

All first-time dislocators require imaging to stratify risk and determine whether they have high-risk features that might benefit from early surgical intervention. 7

• Risk factors for recurrence include: younger age, skeletal immaturity, contralateral instability, trochlear dysplasia, patella alta, increased tibial tubercle-trochlear groove distance, and increased patellar tilt 7
• Arrange orthopedic follow-up within 1-2 weeks for treatment planning and rehabilitation initiation 3
• Most recurrent dislocations occur within the first year after injury 9

Critical Pitfalls to Avoid

• Do not dismiss vomiting as purely pain-related without obtaining imaging—it may indicate a displaced osteochondral fragment requiring surgery 1
• Do not immobilize rigidly for more than 10 days, as this impairs mobility and increases stiffness 1
• Do not skip the patellofemoral (axial) radiographic view, as it is essential for evaluating fractures and subluxation 5
• Do not assume all patellar dislocations are the same—imaging is mandatory for risk stratification 7
• Do not add lateral release to arthroscopic treatment, as this increases recurrence rates (73% vs 93% good/excellent results without lateral release) 9