01Approach to the Critical Patient/attcp55

Primary survey and limb threat

›Immediate priorities

›Airway and breathing compromise from polytrauma context

›Hemorrhagic shock screen for high energy mechanism

›Analgesia before repeated knee manipulation

›Open fracture pathway if skin breach near patella

›Limb threat checks

›Distal perfusion

›Dorsalis pedis pulse

›Posterior tibial pulse

›Capillary refill

›Doppler signal if pulses equivocal

›Distal motor

›Ankle dorsiflexion

›Great toe extension

›Ankle plantarflexion

›Distal sensory

›Deep peroneal distribution

›Superficial peroneal distribution

›Tibial distribution

›Saphenous distribution

›Compartment syndrome screen

›Pain out of proportion

›Pain with passive toe stretch

›Progressive tense swelling

›New paresthesia or weakness

›Extensor mechanism threat

›Inability to perform straight leg raise

02History/hx36

Mechanism and context

›Injury context

›Direct blow to anterior knee

›Dashboard injury pattern

›Fall onto flexed knee

›Indirect eccentric quadriceps contraction

›Jump landing

›Sudden deceleration

›High energy trauma context

›Motor vehicle collision

›Pedestrian struck

›Fall from height

›Timeline

›Time since injury

›Prior reduction attempts

›Progressive swelling timeline

Function and red flags

›Functional status

›Immediate ability to bear weight

›Immediate ability to actively extend knee

›Straight leg raise ability

›Pain and swelling features

›Rapid hemarthrosis

›Pain out of proportion

›Progressive tightness

›Open injury features

›Laceration over patella

›Contamination concern

03Physical Exam/exam35

Knee focused exam

›Inspection and skin

›Swelling and effusion

›Ecchymosis anterior knee

›Skin tenting or blanching

›Laceration and wound contamination

›Palpation

›Patellar tenderness

›Palpable step off

›Palpable patellar gap

›Quadriceps tendon tenderness

›Patellar tendon tenderness

›Range of motion and function

›Straight leg raise

›Inability suggests extensor mechanism disruption

›Pain limited but intact extension suggests continuity

›Active knee extension against gravity

›Passive range limits from effusion

›Effusion and hemarthrosis

›Large tense effusion

›Patellar ballotment

Associated injuries

›Ligament and joint line screening when tolerated

›Medial joint line tenderness

›Lateral joint line tenderness

›Varus and valgus laxity in extension suspicion

›ACL and PCL concern with high energy mechanism

›Hip and ankle screen

04Differential Diagnosis/ddx28

Traumatic knee conditions

›Differential set

›Patellar dislocation with osteochondral fracture

›Lateral tenderness and apprehension

›Medial patellofemoral ligament tenderness

›Quadriceps tendon rupture

›Suprapatellar gap

›Low riding patella possible

›Patellar tendon rupture

›High riding patella

›Inability to extend knee

›Tibial plateau fracture

›Joint line tenderness

›Inability to bear weight

›Distal femur fracture

›Supracondylar tenderness

›Deformity or shortening

›Knee hemarthrosis from intra articular injury

›ACL tear

›Osteochondral fracture

Mimics and chronic variants

›Mimics

›Bipartite patella

›Smooth corticated fragment

›Superolateral location

›Patellofemoral arthritis flare with effusion

›Prepatellar bursitis after trauma

05Laboratory Tests/lt21

Routine labs and selective use

›Minimal lab strategy

›No routine labs for isolated closed stable fracture

›Labs driven by operative pathway or systemic risk

›Preoperative or significant injury labs

›Complete blood count for anemia or open fracture

›Hemoglobin trend if major bleeding concern

›Leukocytosis nonspecific for trauma stress

›Basic metabolic panel for sedation or comorbidity

›Creatinine for medication selection

›Electrolytes for peri sedation risk

›Coagulation studies for anticoagulant use or planned OR

›INR interpretation for warfarin

›Anti Xa only if protocolized for LMWH

›Rhabdomyolysis or crush context

›Creatine kinase for prolonged entrapment

›Renal injury risk linkage

›IV fluid trigger by protocol

Open fracture and infection context

›Open injury adjuncts

›Type and screen if operative likely

›Lactate only for systemic shock evaluation

›Cultures not recommended pre antibiotics in ED for uncomplicated open fracture

06Diagnostic Tests/dt43

Scoring Systems

›Classification and implications

›AO OTA patella fracture framework

›Extra articular versus partial articular versus complete articular grouping concept

›Comminution as operative planning modifier

›Gustilo Anderson open fracture classification

›Grade I small clean wound low energy

›Grade II wound size greater soft tissue injury

›Grade III high energy extensive soft tissue damage

›Antibiotics and urgent orthopedics tied to grade

Radiographs

›X-ray strategy

›Standard knee views

›AP

›Lateral

›Sunrise or Merchant view

›Vertical fracture detection

›Sunrise view improves sensitivity versus AP alone

›CT if persistent suspicion

›Alignment and displacement documentation

›Fracture gap measurement

›Articular step off measurement

›Patella height assessment for tendon disruption

›Nonoperative candidacy radiographic thresholds

›Minimally displaced definition

›Fracture gap less than 3 mm reported in narrative review

›Articular step off less than 2 to 3 mm reported in narrative review

›Post immobilization imaging

07Disposition/dispo26

ED disposition pathways

›Discharge criteria

›Closed injury

›Neurovascularly intact

›Pain controlled on oral regimen

›Extensor mechanism intact

›Minimal displacement on imaging

›Safe ambulation with aids

›Admission criteria

›Open fracture

›Extensor mechanism disruption

›Displacement likely requiring fixation

›Uncontrolled pain

›Inability to mobilize safely

›Polytrauma or unsafe social situation

›Transfer criteria

›Open fracture requiring orthoplastic capability

›Urgent fixation need without local coverage

›Vascular injury concern

›Compartment syndrome concern

Follow up and timing

›Follow up targets

›Orthopedics within 3 to 7 days for closed stable fractures

›Same day or next day orthopedics for suspected operative fractures

›Earlier review for worsening swelling or skin compromise

›Mobility instructions

›Weight bearing status per stability and immobilization plan

›Crutches or walker fitting and training

08Treatment/t76

Immediate life-saving interventions

›Life threats and escalation

›Trauma resuscitation pathway for high energy injury

›If open fracture suspected then antibiotics and tetanus pathway without delay

›If threatened skin then urgent orthopedics escalation

›If neurovascular deficit then immediate ortho and vascular escalation

Immobilization and Splinting

›Immobilization choice

›Knee immobilizer in extension

›Preferred for most stable patellar fractures

›Allows skin checks and swelling accommodation

›Hinged knee brace locked in extension

›Option when early supervised ROM planned

›Posterior long leg splint

›Option for severe pain or noncompliance concern

›Principles

›Knee extension position to reduce extensor mechanism tension

›Swelling phase avoidance of circumferential casting

›Post application neurovascular recheck

›Two finger tightness check at straps

›Skin protection

›Padding at malleoli and heel

›Padding at popliteal fossa strap edges

›Pressure point reassessment after ambulation trial

Reduction

›Reduction considerations

›No routine reduction for isolated patellar fracture fragments

›If patellar dislocation present then reduction pathway

09Special Populations/sp38

Pregnancy

›Pregnancy considerations

›Maternal stabilization priority

›Trauma pathway alignment

›Left lateral tilt if hypotension concern

›Imaging safety

›Knee radiographs low fetal dose with shielding

›CT only if clinically required for maternal care

›Analgesia selection

›Acetaminophen preferred

›NSAID avoidance in later gestation per obstetric guidance

›VTE risk increased in pregnancy

›Lower threshold for prophylaxis discussion if immobilized

Geriatric

›Older adult considerations

›Fragility mechanism common

›Fall from standing height

›Osteoporosis evaluation trigger

›Higher functional risk from immobilization

›Deconditioning and falls risk

›Home supports assessment

›Medication risks

›Opioid delirium risk

›NSAID renal and GI risk

›Admission threshold lower

›Unsafe mobility

›Inadequate pain control

10Background/b37

Epidemiology

›Epidemiology facts

›Patellar fractures uncommon compared with other lower limb fractures

›Approximately 20 to 30 percent reported operative treatment rates in cohort data

›Surgical treatment proportion 26 percent in a large cohort cited by AO Foundation solution page

›Mechanisms

›Direct trauma common

›Indirect eccentric contraction less common

Pathophysiology

›Pathophysiology essentials

›Patella as sesamoid bone in quadriceps tendon

›Extensor mechanism continuity as primary functional determinant

›Intra articular fracture with hemarthrosis common

›Force vector to pattern mapping

›Transverse fracture from tensile failure during quadriceps contraction

›Comminuted fracture from direct blow with articular cartilage injury risk

›Vertical fracture from compressive or direct force often stable if extensor intact

›Complication mechanisms

›Post traumatic patellofemoral arthritis from articular incongruity

›Stiffness from prolonged immobilization

›Symptomatic hardware after fixation

Therapeutic Considerations

›Treatment rationale

›Primary goal restoration of extensor mechanism and articular congruity

›Nonoperative success predictors

›Intact straight leg raise

›Minimal displacement thresholds

›Fracture gap less than 3 mm

11Patient Discharge Instructions/pdi27

copy discharge instructions

›Discharge instructions bundle

›Brace or splint

›Keep knee straight in immobilizer unless orthopedics instructed otherwise

›Keep splint clean and dry

›Do not adjust tight straps without reassessment if numbness occurs

›Swelling control

›Elevation above heart as much as possible first 48 hours

›Ice 15 to 20 minutes at a time several times daily

›Pain plan

›Acetaminophen as directed on label or prescription

›NSAID only if safe for kidneys stomach and bleeding risk

›Opioid only if prescribed and avoid driving

›Activity

›Weight bearing only as instructed

›Crutches or walker use until safe gait

›No sports running or jumping until cleared

›Return to ED now if

›New numbness or weakness in foot

›Foot becomes cold pale or blue

›Rapidly worsening pain despite medication

›Increasing tightness or severe swelling in leg

›Brace feels too tight and symptoms do not improve after loosening straps

›Fever or wound drainage

›Any concern for open wound worsening

›Follow up

›Orthopedics appointment timing as provided

›Earlier review for worsening swelling or skin changes

12References/r8

Clinical guidelines and key sources

›Patellar fracture displacement thresholds and nonoperative criteria

›Narrative review defining minimally displaced gap less than 3 mm and step off less than 2 to 3 mm

›StatPearls summary of nonoperative criteria and extensor mechanism priority

›Practical guidelines paper citing operative indications step off greater than 2 mm and displacement thresholds

›Open fracture initial management timing

›BOAST open fracture guidance antibiotics ideally within 1 hour

›General ED orthopedic reference

›Orthobullets patella fracture summary for immobilization and indications

Evidence & Review

Evidence & Review