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Approach to the Critical Patient
Triage and Immediate Priorities
Initial priorities
Hemodynamic instability triggers alternate diagnosis and trauma evaluation
Major hemorrhage uncommon in isolated patella fracture
Severe pain out of proportion trigger compartment syndrome and open injury evaluation
Escalate analgesia and urgent orthopedic consultation if suspected
Open fracture triggers
If open wound over patella with visible deep tissue then treat as open fracture
If gross contamination then urgent irrigation and operative planning
Neurovascular and Limb Threat Screen
Limb threat screen
Distal pulses and perfusion
If diminished pulses then knee dislocation pathway and urgent vascular imaging
Motor function
Ankle dorsiflexion and plantarflexion
Great toe extension
Sensory function
Peroneal nerve distribution
Tibial nerve distribution
Compartment syndrome features
Pain with passive stretch of toes and ankle
Tense compartments and escalating analgesic requirement
Early Stabilization
Stabilization bundle
Knee immobilizer or posterior long leg splint in full extension
Splinting goal extensor mechanism protection
Non weight bearing until imaging and extensor mechanism assessment completed
Weight bearing as tolerated in extension only if stable nondisplaced fracture and intact extensor mechanism
Ice and elevation
Skin checks for pressure injury in immobilizer
Analgesia strategy
Multimodal nonopioid first line when appropriate
Opioid for breakthrough severe pain with short course planning
History
Mechanism and Functional Status
Mechanism features
Direct blow
Dashboard injury
Fall onto flexed knee
Indirect eccentric contraction
Sudden quadriceps contraction with knee flexed
Slip with attempted prevention of fall
High energy trauma markers
Multiple injuries
Anticipated comminution or open injury
Functional clues
Inability to actively extend knee
Extensor mechanism disruption concern
Inability to perform straight leg raise
Patellar tendon or quadriceps tendon injury concern
Immediate swelling
Hemarthrosis pattern
Risk Factors and Modifiers
Patient factors
Osteoporosis and fragility mechanism
Lower energy mechanism still associated with fracture in older adults
Prior knee surgery
Hardware and altered anatomy affecting imaging and management
Anticoagulant or antiplatelet therapy
Larger hemarthrosis and bleeding risk
Diabetes and peripheral vascular disease
Higher wound complication risk
Smoking
Delayed union risk
Injury context
Open wound timing and contamination source
Farm or soil contamination raises clostridial concern
Tetanus immunization status
Unknown or incomplete immunization triggers prophylaxis
Associated injuries symptoms
Hip pain and inability to bear weight
Ankle pain and foot numbness
Physical Exam
Knee Focused Exam
Knee findings
Inspection
Swelling and effusion
Ecchymosis and abrasion pattern
Open wound over anterior knee
Palpation
Patellar tenderness and crepitus
Palpable defect and step off
Medial and lateral joint line tenderness
Effusion characteristics
Large tense effusion consistent with hemarthrosis
Lipohemarthrosis suspicion with intraarticular fracture
Extensor Mechanism Assessment
Extensor mechanism
Straight leg raise
If unable then extensor mechanism disruption until proven otherwise
Active knee extension against gravity
Lag suggests disruption or pain inhibition
Patellar tendon continuity
Inferior pole tenderness and gap concern
Quadriceps tendon continuity
Suprapatellar tenderness and gap concern
Neurovascular and Skin
Distal assessment
Pulses
Dorsalis pedis and posterior tibial pulses
Capillary refill and temperature
Delayed refill triggers vascular concern
Sensation
Peroneal nerve distribution over dorsum of foot
Tibial nerve distribution plantar foot
Motor
Ankle dorsiflexion and plantarflexion
Toe extension
Soft tissue
Skin tenting and threatened skin
Urgent orthopedic consultation trigger
Blistering and severe contusion
Higher infection risk with surgery timing considerations
Differential Diagnosis
Knee Trauma Differential
Life threats and limb threats
Knee dislocation with vascular injury
Popliteal artery injury risk with normal initial pulses
Open fracture of patella
Infection risk and operative urgency
Compartment syndrome of leg
Disproportionate pain and tense compartments
Common mimics
Quadriceps tendon rupture
Inability to extend knee with suprapatellar gap
Patellar tendon rupture
Patella alta and inferior pole tenderness
Patellar dislocation with osteochondral fracture
Lateral patellar apprehension and hemarthrosis
Tibial plateau fracture
Lateral joint line tenderness and inability to bear weight
Distal femur fracture
Above knee pain and deformity
Meniscal tear and ligament injury
Locking or instability symptoms
Coding Anchors
Administrative codes to consider
ICD-10 patella fracture category S82.0
Specify laterality and open versus closed
SNOMED CT patella fracture concept
Use local terminology mapping for EHR problem list
Laboratory Tests
Baseline and Perioperative Testing
Labs when indicated
Open fracture or planned surgery
Complete blood count for anemia and infection baseline
Electrolytes and creatinine for perioperative planning
Coagulation studies for anticoagulant use or liver disease
Significant hemarthrosis with anticoagulation
Hemoglobin trend if clinical concern for bleeding
Coagulation studies to guide reversal planning
Pregnancy possibility
Urine or serum pregnancy test before ionizing imaging and medications
Infection and Inflammatory Evaluation
Infection workup when clinically suspected
Septic arthritis concern
C reactive protein and erythrocyte sedimentation rate supportive but nonspecific
Arthrocentesis cell count and culture if atraumatic fever and severe pain
Open wound contamination
Wound culture not recommended prior to operative debridement
Point of Care Testing
POC testing
Glucose in diabetic patients with acute injury
Hyperglycemia associated with wound complications
Lactate only if systemic illness or shock features
Not routine for isolated patella fracture
Diagnostic Tests
Scoring Systems
Imaging decision tools and classification
Ottawa Knee Rule for radiographs
Age 55 years or older
Isolated patellar tenderness
Fibular head tenderness
Inability to flex knee to 90 degrees
Inability to bear weight 4 steps immediately and in ED
Pittsburgh Knee Rule for radiographs
Blunt trauma or fall mechanism
Age younger than 12 years or older than 50 years
Inability to walk 4 weight bearing steps in ED
Patella fracture pattern classification
Transverse fracture pattern
Vertical fracture pattern
Comminuted fracture pattern
Inferior pole avulsion fracture pattern
Osteochondral fracture pattern
Pediatric sleeve fracture pattern
AO OTA classification patella
Patella segment 34
Partial articular and complete articular pattern descriptors
MRI
MRI role
Occult fracture with persistent pain and negative radiographs
Bone marrow edema pattern and cartilage injury identification
Extensor mechanism soft tissue injury evaluation
Quadriceps tendon tear characterization
Patellar tendon tear characterization
Osteochondral injury evaluation after patellar dislocation
Loose body detection for operative planning
Limitations
Reduced availability in ED setting
Metal artifact if prior hardware
CT
CT role
Comminuted fracture characterization
Articular surface step off delineation
Fragment mapping for surgical planning
Suspected intraarticular extension with unclear radiographs
Lipohemarthrosis correlation
3D reconstruction support for operative planning
Useful for multifragmentary patterns
Radiation considerations
Avoid routine CT in clearly nondisplaced fractures with stable management plan
Ultrasound
Ultrasound role
POCUS extensor mechanism assessment
Patellar tendon continuity and partial tear features
Quadriceps tendon continuity and partial tear features
Effusion assessment
Large hemarthrosis confirmation when exam limited by pain
Guidance for arthrocentesis when performed
Sterile technique and landmark confirmation
Limitations
Operator dependence
Limited bony detail compared with radiographs and CT
Disposition
Admission and Transfer Criteria
Higher level care indications
Open fracture
Admission for antibiotics and operative management
Extensor mechanism disruption
Urgent orthopedic evaluation for operative planning
Displaced fracture with articular incongruity
Operative consideration and pain control needs
Polytrauma or inability to safely ambulate
PT and OT needs and social disposition barriers
Neurovascular compromise
Emergent vascular and orthopedic management
ED Discharge Criteria
Discharge requirements
Stable vitals and pain controlled on oral regimen
Multimodal plan established
Closed fracture with intact extensor mechanism
Straight leg raise intact or active extension intact
Acceptable alignment on imaging for nonoperative plan
Nondisplaced or minimally displaced per local orthopedic criteria
Safe mobility plan
Crutches or walker training completed
Weight bearing instructions understood
Follow up arranged
Orthopedics within 5 to 10 days or sooner if displaced pattern
Treatment
Immobilization and Activity
Nonoperative pathway
Indications
Intact extensor mechanism
Nondisplaced or minimally displaced fracture pattern
Immobilization in full extension
Knee immobilizer or cylinder cast based on swelling and compliance
Skin checks daily
Weight bearing plan
Weight bearing as tolerated in extension for stable patterns
Non weight bearing if uncertain stability or severe pain
Early motion plan with orthopedics
Progressive range of motion after initial immobilization period per specialist plan
Analgesia
Multimodal analgesia
Acetaminophen
1000 mg PO every 6 to 8 hours
Maximum 3000 mg per day in most adults
Lower maximum in chronic liver disease and heavy alcohol use
Ibuprofen
400 mg PO every 6 to 8 hours
Maximum 2400 mg per day
Avoid in significant renal disease and active GI bleeding
Naproxen
500 mg PO once then 250 mg PO every 6 to 8 hours
Maximum 1000 mg per day
Avoid in third trimester pregnancy
Ketorolac
15 mg IV once
Avoid in renal impairment and high bleeding risk
Avoid repeated dosing without clear indication
Oxycodone
5 mg PO every 6 hours as needed
Short course and lowest effective dose
Avoid with significant sedation risk and concomitant CNS depressants
Hydromorphone
0.5 mg IV every 2 to 3 hours as needed
Continuous monitoring if repeated dosing
Use caution in older adults and sleep apnea
Hemarthrosis and Procedural Options
Effusion management
Symptomatic hemarthrosis
If severe pain from tense effusion then ultrasound guided arthrocentesis consideration
Avoid aspiration through overlying cellulitis or open wound
Local anesthesia options
Lidocaine 1 percent infiltration
Avoid intraarticular steroid in acute fracture setting
Antibiotics and Tetanus for Open Injury
Open fracture prophylaxis
Cefazolin
2 g IV every 8 hours
Increase to 3 g IV every 8 hours if very high body mass
Start as soon as possible after recognition
Severe cephalosporin allergy
Clindamycin 900 mg IV every 8 hours
MRSA risk context consideration
Gross contamination or farm injury
Add gentamicin 5 mg per kg IV once
Renal dosing adjustment required
Tetanus prophylaxis
If unknown or fewer than 3 prior doses then tetanus immunoglobulin plus vaccine
If 3 or more prior doses then booster based on wound type and time since last dose
Operative Pathway Overview
Operative indications overview
Disrupted extensor mechanism
Inability to perform straight leg raise not explained by pain alone
Displaced fracture and articular incongruity
Step off and gap exceeding local orthopedic thresholds
Open fracture
Irrigation and debridement and fixation planning
Large osteochondral fragment or loose body
Mechanical symptoms or joint block
Fixation concepts
Tension band constructs for transverse fractures
Converts tensile forces to compressive forces in flexion
Screws and cerclage options for comminution
Fragment specific fixation
Partial patellectomy for nonreconstructible inferior pole
Extensor mechanism restoration priority
Thrombosis and Immobilization Considerations
VTE risk considerations
Lower limb immobilization increases VTE risk
Individual risk stratification for prophylaxis decision
High risk features
Prior VTE
Active cancer
Major trauma or prolonged non weight bearing
Prophylaxis planning
Coordinate with orthopedics or primary care for outpatient plan when indicated
Special Populations
Pregnancy
Pregnancy considerations
Imaging strategy
Radiographs acceptable with shielding when clinically indicated
Avoid unnecessary CT and consider MRI if needed for occult injury
Analgesia considerations
Acetaminophen preferred first line
NSAID avoidance in third trimester
VTE risk
Pregnancy hypercoagulability with immobilization increases VTE concern
Early mobilization emphasis when safe
Geriatric
Older adult considerations
Fragility fracture context
Low energy mechanism still significant injury
Osteoporosis evaluation and fall risk counseling
Medication safety
NSAID renal and GI risk higher
Opioid delirium and fall risk
Functional discharge planning
Mobility aids and home safety assessment needs
Pediatrics
Pediatric considerations
Sleeve fracture recognition
Cartilaginous avulsion may appear subtle on radiographs
High suspicion with extensor lag and inferior pole tenderness
Imaging and sedation considerations
Minimize radiation exposure
MRI or ultrasound for occult sleeve fracture when needed
Weight based analgesia
Acetaminophen 15 mg per kg PO every 6 hours
Ibuprofen 10 mg per kg PO every 6 to 8 hours
Background
Epidemiology
Epidemiology
Typical mechanism distribution
Direct blow and fall common causes
Indirect eccentric contraction less common but important
Injury pattern
Intraarticular involvement common due to patella articular surface
Open fracture risk with anterior subcutaneous location
Associated injuries
Ligament and cartilage injury risk in high energy mechanisms
Patellar dislocation association with osteochondral fragments
Pathophysiology
Pathophysiology
Extensor mechanism role
Patella increases quadriceps lever arm and knee extension strength
Disruption causes loss of active extension
Fracture mechanics
Direct trauma causes comminution and soft tissue injury
Indirect contraction causes transverse patterns
Hemarthrosis mechanism
Intraarticular bleeding from cancellous bone and synovial irritation
Therapeutic Considerations
Treatment principles
Goals
Restore extensor mechanism continuity
Maintain articular congruity to reduce post traumatic arthritis risk
Nonoperative rationale
Stable nondisplaced fractures heal with immobilization
Early controlled motion reduces stiffness risk when safe
Operative rationale
Displacement increases articular step off and arthritis risk
Extensor disruption requires repair for function restoration
Evidence framing
Clinical decision making primarily orthopedic consensus and cohort outcomes
Imaging decision rules for knee radiographs supported by high sensitivity studies
Patient Discharge Instructions
copy discharge instructions
Discharge instructions
Diagnosis and plan
Patella fracture treated with immobilizer in full extension
Keep immobilizer on except for skin checks as instructed
Activity
Weight bearing instructions as provided
Crutches or walker use until cleared
Swelling and pain care
Ice 15 to 20 minutes at a time several times daily
Elevation above heart level when resting
Medications
Acetaminophen and NSAID schedule if safe for you
Opioid only for severe pain and avoid driving or alcohol
Wound care
Keep any wounds clean and dry
Return immediately for spreading redness or pus
Follow up
Orthopedics appointment within 5 to 10 days or as arranged
Repeat imaging may be needed to confirm alignment
Return to ED now
Increasing pain not controlled with medication
New numbness or weakness in foot
Toes cold or blue or severe swelling of calf
Fever or worsening redness around a wound
Immobilizer too tight or new severe calf pain or shortness of breath
References
Guidelines and Evidence Sources
Core references
Ottawa Knee Rule derivation and validation studies for knee radiograph decision making
High sensitivity for clinically important knee fractures in multiple validations
Pittsburgh Knee Rule validation studies
High sensitivity for knee fracture detection in blunt trauma
Orthopedic trauma references for patella fracture management
AO Foundation surgery reference for patella fracture patterns and fixation concepts
OTA and orthopedic texts on patella fracture indications for operative fixation
Extensor mechanism disruption and displacement as primary operative drivers
Professional Society and Practice Resources
Practice resources
AAOS educational resources for fracture care and rehabilitation principles
Emphasis on function restoration and complication prevention
Emergency medicine references for analgesia and immobilization best practices
Multimodal analgesia and short opioid courses when needed
VTE risk guidance for lower limb immobilization
Individual risk stratification approach for prophylaxis decisions
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.