Patellar dislocationMANAGEMENT

THIGH & KNEE · 12 SECTIONS

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351 items

☷ Legend

01Approach to the Critical Patient/attcp34

Immediate priorities

›Initial stabilization

›ABC stability confirmation

›Hemodynamic instability triggers alternate diagnosis or polytrauma pathway

›High-energy mechanism triggers full lower extremity trauma survey

›Limb threat screen

›Distal perfusion

›Dorsalis pedis pulse

›Posterior tibial pulse

›Capillary refill

›Neurologic function

›Peroneal nerve motor (ankle dorsiflexion, great toe extension)

›Peroneal nerve sensory (dorsum of foot, first web space)

›Tibial nerve motor (plantarflexion)

›Tibial nerve sensory (plantar foot)

›Reduction urgency triggers

›Threatened skin over lateral patella

›Severe pain with fixed deformity

›Neurovascular deficit after injury

›Locked knee concern for osteochondral fragment

›Post-reduction safety checks

›Neurovascular status documented before reduction

›Neurovascular status documented after reduction

›Post-reduction imaging completed before disposition

Consultation and escalation

›Orthopedics escalation triggers

›Irreducible dislocation

›Large osteochondral fracture on imaging

02History/hx24

Mechanism and timing

›Injury context

›Noncontact pivot with valgus and external rotation

›Direct blow to medial patella

›Sports participation

›Timeline

›Time since dislocation event

›Spontaneous reduction versus persistent deformity

›Prior similar episodes

Risk factors and associated injury mapping

›Prior knee pathology

›Previous patellar instability

›Prior surgery to knee

›Generalized ligamentous laxity

›Anatomic predisposition clues

›Patella alta history or prior imaging mention

›Trochlear dysplasia history or prior imaging mention

›Increased femoral anteversion or tibial torsion history

›Symptoms suggesting associated injury

›Immediate hemarthrosis

›Mechanical locking or catching

›Inability to actively extend knee after reduction

›Medial knee pain suggesting MPFL injury

›Bleeding and medication context

›Anticoagulants

›Antiplatelet therapy

03Physical Exam/exam32

Focused knee exam

›Deformity and skin

›Lateral patellar displacement

›Skin tenting or blanching

›Abrasion or laceration

›Effusion and hemarthrosis

›Rapid effusion suggesting osteochondral injury

›Large tense effusion affecting neurovascular exam reliability

›Extensor mechanism integrity

›Active straight leg raise after reduction

›Quadriceps tendon continuity

›Patellar tendon continuity

›Patellar stability maneuvers after reduction

›Patellar apprehension test

›J sign during active extension

›Medial stabilizer tenderness

›MPFL region tenderness at medial patella

›Adductor tubercle region tenderness

Neurovascular and adjacent injury screen

›Distal neurovascular exam

›Dorsalis pedis pulse

›Posterior tibial pulse

›Peroneal sensory distribution

›Tibial sensory distribution

›Ligament and meniscus screen after pain control

›ACL laxity screen

›MCL tenderness

›LCL tenderness

04Differential Diagnosis/ddx17

Knee injury mimics and co-injuries

›Alternative diagnoses

›ACL rupture (ICD-10 S83.51)

›MCL sprain (ICD-10 S83.41)

›Meniscal tear (ICD-10 S83.2)

›Patellar tendon rupture (ICD-10 S86.81)

›Quadriceps tendon rupture (ICD-10 S76.11)

›Associated injuries with patellar dislocation

›Osteochondral fracture of patella or lateral femoral condyle (ICD-10 S82.0 with intra-articular fragment as applicable)

›MPFL tear (SNOMED CT concept patellofemoral ligament injury)

›Patellar sleeve fracture in pediatrics (ICD-10 S82.0)

›High-risk alternative injury patterns

›Tibiofemoral knee dislocation (ICD-10 S83.10)

›Tibial plateau fracture (ICD-10 S82.14)

Coding alignment

›Patellar dislocation coding

›ICD-10 S83.0 dislocation of patella

›SNOMED CT patellar dislocation

›Lateral patellar dislocation as typical direction

05Laboratory Tests/lt13

When labs are useful

›Baseline tests for procedural sedation pathway

›Glucose for altered mental status or diabetes concern

›Pregnancy test in patients with pregnancy potential before sedation imaging choices

›Targeted electrolytes when significant comorbidity or prolonged fasting with vomiting

›Bleeding and anticoagulation context

›INR for warfarin use with large hemarthrosis concern

›CBC for significant swelling with anemia concern

Usually not indicated

›Uncomplicated isolated patellar dislocation

›No routine labs required

›Pain control and imaging drive care

PITFALLS

›Lab limitations

›Normal labs do not exclude osteochondral fracture

›Hemarthrosis assessment is clinical and imaging-based rather than lab-based

06Diagnostic Tests/dt43

Scoring Systems

›Decision support and measurement tools

›No validated ED decision rule to exclude osteochondral injury

›Radiographic risk factor measurements used for recurrence risk stratification

›Patella alta indices (Insall Salvati ratio, Caton Deschamps index)

›Trochlear dysplasia features (Dejour classification on lateral imaging and MRI)

›Tibial tubercle to trochlear groove distance (TT TG) on CT or MRI

›Clinical recurrence risk factors

›Age younger than 20 years associated with higher recurrence

›Prior dislocation associated with higher recurrence

Radiographs

›X-ray evaluation

›Pre-reduction imaging when diagnosis uncertain and no limb threat

›Knee AP view

›Knee lateral view

›Patellar sunrise or Merchant view when tolerated

›Post-reduction imaging expectations

›Alignment confirmation

›Osteochondral fragment screen

›Loose body screen

›Radiographic findings supporting lateral dislocation

›Lateral patellar displacement on axial view

›Effusion on lateral view

›Radiograph limitations

›Poor sensitivity for chondral only injury

›Small osteochondral fragments may be missed

MRI

›MRI indications

07Disposition/dispo16

Discharge criteria

›Safe outpatient management

›Successful reduction

›Neurovascularly intact after reduction

›Pain controlled with oral regimen

›Able to ambulate with brace and crutches

›No large displaced osteochondral fragment on imaging

›No extensor mechanism disruption

Admission or urgent specialty pathway

›Observation or admission considerations

›Uncontrolled pain requiring parenteral analgesia

›Inability to ambulate safely

›Social barriers preventing safe discharge plan

›Urgent orthopedics management

›Irreducible dislocation

›Large osteochondral fracture

›Loose body with locked knee

›Persistent extensor mechanism failure

08Treatment/t87

Immediate life-saving interventions

›Immediate stabilization

›Vascular compromise pathway

›Immediate reduction attempt if dislocation suspected and pulses absent

›Post-reduction pulse reassessment

›If persistent ischemia then emergent orthopedics and vascular consultation

›Analgesia for severe pain while preparing reduction

›Non-opioid analgesia options

›Acetaminophen PO 1000 mg once

›Ibuprofen PO 400 mg once

›Opioid titration options

›Fentanyl IV 0.5 to 1 mcg per kg

›Repeat fentanyl IV 0.5 mcg per kg every 5 minutes to effect

›Threatened skin management

›Immediate reduction when skin tenting present

›Avoid repeated forceful attempts

Immobilization and Splinting

›Post-reduction immobilization options

›Knee immobilizer in extension

›Patellar stabilizing brace when available

›Hinged knee brace locked in extension initially when prescribed by specialist

›Immobilization principles

›Extension position reduces lateral translation risk acutely

›Neurovascular reassessment after brace placement

›Avoid circumferential casting in acute swelling phase

›Mobility support

›Crutches

›Weight bearing as tolerated if stable and pain controlled

›Non weight bearing if severe pain or instability

Reduction

›Indications for reduction

›Persistent lateral patellar displacement

›Severe pain with visible deformity

›Threatened skin

›Contraindications or caution triggers

›Suspected knee dislocation rather than patellar dislocation

›Open injury

›Gross instability suggesting major ligament injury

›Analgesia and anesthesia options

›Minimal sedation pathway when cooperative

›IV opioid only

›Fentanyl IV 0.5 to 1 mcg per kg

›Re-dose as needed

›Regional anesthesia options

›Adductor canal block or femoral nerve block

›Ropivacaine 0.5% 15 to 20 mL

›Maximum ropivacaine 3 mg per kg

›Alternative local anesthetic

›Bupivacaine 0.25% 15 to 20 mL

›Maximum bupivacaine 2.5 mg per kg

›Procedural sedation pathway when needed

›Monitoring and airway readiness

›Cardiac monitor

›Continuous pulse oximetry

›Capnography when available (ACEP Level B)

›Suction available

›Bag valve mask available

›Ketamine option

›Ketamine IV 1 to 2 mg per kg

›Additional ketamine IV 0.5 mg per kg as needed

›Propofol option

›Propofol IV 0.5 to 1 mg per kg

›Additional propofol IV 0.25 to 0.5 mg per kg as needed

›Etomidate option

›Etomidate IV 0.1 to 0.2 mg per kg

›Additional etomidate IV 0.05 mg per kg as needed

›Technique principles

›Hip flexion to relax quadriceps

›Slow knee extension while applying medial pressure to patella

›Gentle sustained force

›Stop if severe resistance or concern for alternate injury

›Post-reduction requirements

›Immediate neurovascular re-check

›Active extension check

›Post-reduction radiographs

›Brace placement in extension

›Failed reduction pathway

›If irreducible then urgent orthopedics

›If worsening neurovascular status then emergent escalation

›If mechanical block then concern for loose body and urgent imaging

Open fracture medications and timing

›Open injury overlap

›Patellar dislocation rarely open

›If open wound over joint then treat as traumatic arthrotomy pathway

›Antibiotics per open joint protocol

›Tetanus prophylaxis per immunization status

›Urgent orthopedics consultation

DVT prophylaxis when relevant

›VTE risk context

›Isolated patellar dislocation usually low risk

›Consider prophylaxis if prolonged lower limb immobilization with major risk factors

›Follow local protocol for outpatient immobilization prophylaxis

09Special Populations/sp27

Pregnancy

›Pregnancy considerations

›Imaging selection

›Radiographs acceptable with shielding when needed for management

›MRI preferred over CT when feasible for soft tissue and cartilage detail

›Analgesia selection

›Acetaminophen as first-line

›NSAID avoidance in later pregnancy per obstetric guidance

›Sedation considerations

›Obstetrics consultation for advanced gestation when sedation required

›Aspiration risk mitigation

Geriatric

›Older adult considerations

›Lower threshold for imaging for occult fracture

›Higher fall risk and mobility needs at discharge

›Medication sensitivity

›Opioid delirium risk

›NSAID renal and GI risk

›Osteoporosis context

›Concomitant fracture risk with low-energy mechanism

Pediatrics

›Pediatric considerations

›Higher recurrence risk after first dislocation

›Growth plate injury screening

›Patellar sleeve fracture concern

›Physeal injury concern around knee after trauma

›Weight-based dosing

›Ibuprofen PO 10 mg per kg

10Background/b25

Epidemiology

›Frequency and patterns

›Lateral patellar dislocation most common direction

›Higher incidence in adolescents and young adults

›Sports-related and noncontact pivot mechanisms common

›Reported recurrence rates range approximately 15% to 60% depending on age and anatomy

Pathophysiology

›Injury mechanics

›Lateral translation with valgus and external rotation

›MPFL as primary restraint to lateral translation in early flexion

›Typical injury pattern

›MPFL tear at medial patella or femoral attachment

›Bone bruise medial patella and lateral femoral condyle

›Complication mechanisms

›Osteochondral fracture from shear at patellofemoral contact

›Loose body leading to mechanical block

›Recurrent instability from anatomic risk factors

Therapeutic Considerations

›Reduction rationale

›Pain relief

›Skin compromise prevention

›Restoration of patellofemoral congruity

›Immobilization versus early motion

›Short initial immobilization often used for comfort and soft tissue healing

›Early quadriceps strengthening and VMO focus reduces recurrent instability risk

›Surgical consideration rationale

›Large osteochondral fragment fixation or removal

›Recurrent instability with significant anatomic predisposition

11Patient Discharge Instructions/pdi25

Copy discharge instructions

›Discharge care plan

›Brace use

›Knee immobilizer or patellar stabilizing brace worn continuously except hygiene as directed

›Keep knee in extension until follow-up unless instructed otherwise

›Activity and mobility

›Crutches as needed

›Weight bearing as tolerated if stable and pain controlled

›Avoid pivoting, running, jumping until cleared

›Swelling control

›Elevation above heart when resting

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

›Pain control

›Acetaminophen as directed on label

›Ibuprofen as directed on label if safe for patient

›Follow-up timing

›Sports medicine or orthopedics follow-up within 3 to 7 days

›Earlier follow-up if recurrent instability or significant effusion

›Return to ED now

›Increasing pain not controlled with medication

›New numbness or weakness in foot

›Foot becoming cold or pale

›Increasing swelling with tight brace and worsening pain

›Inability to extend knee after reduction

›Knee locking or inability to bear weight that is worsening

›Fever or spreading redness if wound present

12References/r8

Clinical guidelines and evidence sources

›Core references

›ACEP clinical policy and procedural sedation guidance (capnography support commonly Level B)

›AAOS and sports medicine society guidance on patellar instability evaluation and management

›Orthopedic literature on MPFL injury patterns and osteochondral fracture association

›Coding references

›ICD-10 S83.0 dislocation of patella

›SNOMED CT patellar dislocation concept

›Internal build spec :contentReference[oaicite:0]{index=0}

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed March 6, 2026

SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.