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Patellar dislocation
Shoulder & Clavicle
AC separation
Biceps tendon rupture
Clavicle fracture
Humerus proximal fracture
Rotator cuff tear
Scapular fractures
Shoulder dislocations
SLAP tear
Sternoclavicular dislocation
Arm & Elbow
Compartment syndrome (anterior, lateral, deep - superficial posterior)
Coronoid process fracture
Elbow dislocations
Epicondylar fracture
Humeral shaft fracture
Intercondylar and condylar region fracture
Olecranon fracture
Radial head fracture (Mason I-IV)
Supracondylar fracture (pediatric and adult)
Triceps tendon rupture
Forearm, Wrist & Hand
Carpal bones fractures
Carpal dislocations and ligament injuries
Distal radius and ulna fracture
Fight bite (human bite over MCP)
Finger dislocations by joint
Finger open fractures - amputations
Forearm fractures
Hand and finger tendon and ligament injuries
Hand tendon injuries
Metacarpal fractures
Nail bed injuries
Phalangeal fractures
Tuft fracture
Spine
Cervical spine fracture (C1-C7)
Cord syndromes
Sacrum and coccyx fracture
Thoracic and lumbar spine fracture
Pelvis & Hip
Acetabular fractures
Hip dislocations
Pelvis fractures
Proximal femur fractures
Thigh & Knee
Distal femur fractures
Femoral shaft fractures
Knee dislocation
Knee ligament injuries
Patellar dislocation
Patellar fracture
Patellar tendon rupture
Pes anserine bursitis
Prepatellar bursitis
Quadriceps tendon rupture
Tibial plateau fracture
Tibial spine fracture
Tibial tubercle fracture
Leg & Shin
Achilles tendon rupture
Fibular shaft fracture
Proximal fibula fracture
Stress fracture (tibia-fibula)
Tibial and Fibular shaft fracture
Tibial shaft fracture
Toddler's fracture
Ankle
Ankle dislocation
Ankle fractures
Ankle sprain
Maisonneuve fracture (proximal fibula and syndesmosis)
Peroneal tendon dislocation or tear
Peroneal tendon tear or dislocation
Subtalar dislocation
Syndesmotic injury (high ankle sprain)
Foot
Calcaneus fracture
Cuboid fracture
Cuneiform fractures
Dancer's fracture (5th MT spiral shaft)
Jones fracture (5th MT base - metadiaphyseal junction)
Lisfranc injury (tarsometatarsal dislocation)
March fracture (metatarsal stress fracture)
Metatarsal fractures (1st-5th)
Navicular fracture
Plantar fascia rupture
Talus fracture
Tibialis posterior tendon dysfunction
Toe dislocations
Patellar dislocation
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Clinical Assessment Checklist
Browse categories and answer follow-up questions to refine your symptom profile.
Approach to the Critical Patient
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
Intra-articular loose body with mechanical block
Persistent instability after reduction
Recurrent dislocation with significant anatomic risk factors
Open injury
Immediate transfer triggers
▶
Vascular compromise
Compartment syndrome concern in leg
Polytrauma requiring higher level trauma care
History
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
Physical Exam
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
Joint line tenderness
PITFALLS
Common misses
▶
Occult osteochondral fracture despite reduced patella
Mechanical block from loose body mistaken for guarding
Extensor mechanism injury mistaken for pain limitation
Peroneal nerve symptoms missed without explicit testing
Differential Diagnosis
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
Laboratory Tests
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
Diagnostic Tests
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
▶
First-time dislocation with large effusion or hemarthrosis
Mechanical symptoms (locking, catching)
Persistent pain or instability after reduction
Suspected osteochondral injury with negative radiographs
Expected MRI findings
▶
MPFL injury pattern
Bone bruise pattern (medial patella, lateral femoral condyle)
Osteochondral injury characterization
MRI constraints
▶
Availability and timing often outpatient when stable
Urgent MRI when mechanical block suggests loose body needing surgery
CT
CT indications
▶
Better characterization of osteochondral fragment seen on X-ray
Surgical planning when large intra-articular fragment suspected
MRI contraindicated with ongoing need to characterize bony injury
CT limitations
▶
Limited cartilage detail compared with MRI
Radiation considerations in pediatrics and pregnancy
Disposition
Discharge criteria
Copy
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
Treatment
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
Special Populations
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
Acetaminophen PO 15 mg per kg
Return to sport guidance requires specialist and physiotherapy coordination
Background
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
Patient Discharge Instructions
Copy discharge instructions
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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
References
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
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SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.
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Patellar dislocation