Treatment for Knee Cap (Patellar) Trauma
For knee cap trauma, obtain plain radiographs (anteroposterior and lateral views) as the initial imaging study if the patient meets Ottawa or Pittsburgh rule criteria, followed by appropriate surgical or conservative management based on fracture pattern and severity. 1
Initial Assessment and Imaging Decision
Clinical Decision Rules for Radiography
Apply the Ottawa Knee Rule for patients ≥18 years—obtain radiographs if any of the following are present: 1
- Age ≥55 years
- Isolated patellar tenderness
- Inability to flex knee to 90°
- Inability to bear weight immediately after injury or take 4 steps in the emergency department
- Palpable tenderness over fibular head
Apply the Pittsburgh Decision Rule as an alternative—obtain radiographs if: 1
- Age <12 years or >50 years
- Inability to take four weight-bearing steps in the emergency department
Override clinical decision rules and obtain radiographs immediately for patients with: 1
- Gross deformity
- Palpable mass
- Penetrating injury
- Prosthetic hardware
- Altered mental status (head injury, intoxication, dementia)
- Neuropathy (paraplegia, diabetes)
- Multiple injuries affecting reliable examination
Standard Radiographic Views
Obtain minimum two views (anteroposterior and lateral) with the lateral view at 25-30 degrees of knee flexion to visualize the patella in profile. 1
Add a patellofemoral view specifically for suspected patellar fractures or subluxation/dislocation. 1
Consider a cross-table lateral view with horizontal beam to detect lipohemarthrosis, which indicates intra-articular fracture. 1
Advanced Imaging for Negative Radiographs
When Fracture is Suspected Despite Normal Radiographs
MRI without IV contrast is the preferred next study for adults or skeletally mature children when radiographs are negative but occult fracture or internal derangement is suspected. 1
MRI demonstrates superior accuracy for detecting bone marrow contusions, occult fractures, meniscal injuries, and ligamentous injuries compared to other modalities. 1
CT without IV contrast may be performed as an alternative for detecting radiographically occult fractures, with 100% sensitivity for tibial plateau fractures compared to 83% for radiographs alone. 1
High-Energy Trauma and Knee Dislocation
Significant Trauma Management
For motor vehicle accidents or suspected knee dislocation, obtain both knee radiographs AND CTA of the lower extremity simultaneously, as these are complementary studies. 1
Vascular injury occurs in approximately 30% of posterior knee dislocations and requires prompt identification for limb preservation. 1
CTA is preferred over conventional angiography for suspected vascular injuries due to similar accuracy (high sensitivity and specificity) with less invasiveness. 1
MRA may be performed simultaneously with MRI for comprehensive evaluation of internal derangement and vascular injuries with less morbidity than conventional angiography. 1
Treatment Approach Based on Injury Severity
Hemodynamically Stable Patients
Limb salvage is the recommended approach when hemodynamic stability is maintained, as psychological outcome and quality of life remain superior with successful reimplantation. 1
Functional outcomes are equivalent between immediate and delayed amputation if secondary amputation becomes necessary. 1
Hemodynamic Instability with Vascular Injury
Apply damage control strategy with temporary stabilization using external fixators rather than skeletal traction when definitive osteosynthesis cannot be performed within 24-36 hours. 1
No single severity criterion mandates amputation—decision should be based on multiple factors including: complete traumatic amputation, large tissue loss preventing skin coverage, proven tibial nerve section, multiple fractures with bone loss, and ischemic vascular lesions. 1
Schedule safe definitive orthopaedic surgery as early as possible (typically 36-48 hours to 2 weeks) once clinical stability is achieved through frequent reassessment of hemodynamic status, respiratory function, acid-base status, and coagulation. 1
Common Pitfalls to Avoid
Do not skip documentation of Ottawa or Pittsburgh criteria findings when deciding on radiographs, as this leads to unnecessary imaging or missed fractures. 2
Do not rely solely on ability to bear weight as absence of this finding alone does not exclude fracture—three patients in validation studies had fractures despite negative weight-bearing criterion. 1
Do not order MRI, CT, or ultrasound as initial imaging for acute knee trauma—radiographs remain the appropriate first study. 1
Do not delay vascular assessment in high-energy trauma or suspected dislocation, as popliteal artery injuries require prompt surgical intervention for limb preservation. 1