Knee sprainMANAGEMENT

TRAUMA PRESENTATIONS · 12 SECTIONS

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624 items

☷ Legend

01Approach to the Critical Patient/attcp73

Immediate threats and triggers

›Initial triage priorities

›High-energy mechanism

›Motor vehicle collision

›Fall from height

›Gross deformity

›Suspected dislocation

›Suspected fracture

›Open wound near joint

›Possible open fracture

›Possible traumatic arthrotomy

›Neurovascular compromise

›Absent or diminished distal pulses

›Progressive neurologic deficit

›Compartment syndrome concern

›Pain out of proportion

›Pain with passive stretch

›Systemic toxicity

›Fever

›Hypotension

Focused stabilization and monitoring

›Stabilization targets

›Analgesia adequate for exam

›Multimodal strategy preferred

›Avoid oversedation before stability assessment

›Temporary immobilization

›Knee immobilizer for gross instability

›Posterior splint if severe pain or fracture concern

›Weight-bearing status

›Non-weight-bearing if instability or fracture not excluded

›Protected weight-bearing if stable and fracture excluded

›Neurovascular reassessment

›After immobilization

›After any reduction attempt

Neurovascular and limb-threatening evaluation

›Neurovascular screen

›Vascular status

›Dorsalis pedis pulse

›Posterior tibial pulse

›Capillary refill

›Skin temperature and color

›Motor function

›Ankle dorsiflexion strength

›Great toe extension strength

›Ankle plantarflexion strength

›Sensory function

›Dorsum of foot sensation

›Plantar foot sensation

›Lateral leg sensation

›Knee dislocation risk pathway

›Popliteal artery injury concern

›ABI < 0.9 then urgent vascular imaging

›Hard signs then immediate vascular surgery involvement

›Peroneal nerve injury concern

›Foot drop

›Dorsal foot numbness

Pain control strategy

›Analgesia plan

›Non-opioid first-line

›Acetaminophen oral 15 mg/kg (max 1,000 mg per dose)

›Ibuprofen oral 10 mg/kg (max 600 mg per dose)

›Topical option

›Diclofenac gel for localized pain

›Avoid on broken skin

›Opioid rescue for severe pain

›Oxycodone oral 0.05 to 0.1 mg/kg (max 5 mg per dose) short course only

›Avoid with respiratory depression risk

PEARLS

›Key principles

›Septic arthritis until excluded when hot swollen knee with fever

›Rapid joint destruction risk

›Early ortho involvement when suspected

›Extensor mechanism rupture as time-sensitive diagnosis

›Inability to straight-leg raise

›Requires urgent orthopedic evaluation

›Knee dislocation may reduce spontaneously

›History of gross deformity

›Mandatory vascular assessment

02History/hx68

Symptom profile and timeline

›Presenting features

›Pain location

›Medial joint line pain

›Lateral joint line pain

›Anterior knee pain

›Posterior knee pain

›Onset timing

›Immediate after injury

›Delayed over hours

›Swelling timing

›Immediate hemarthrosis within 2 hours

›Delayed effusion over 12 to 24 hours

›Mechanical symptoms

›Locking

›Catching

›Clicking

›Giving way

Mechanism of injury

›Mechanism clues

›Valgus stress

›MCL injury risk

›ACL risk when pivot

›Varus stress

›LCL injury risk

›Pivot with pop

›ACL injury risk

›Hyperextension

›ACL or PCL injury risk

›Tibial plateau fracture risk

›Direct blow to proximal tibia

›PCL injury risk

›Twisting with foot planted

›Meniscus injury risk

›Patellar lateral displacement

›Patellar dislocation risk

Functional impact

›Functional status

›Weight-bearing ability

›Immediate inability

›Progressive difficulty

›Range of motion limitation

›Inability to fully extend

›Inability to fully flex

›Sports participation

›Cutting and pivoting sports

›Contact sports

Risk factors and modifiers

›Patient factors

›Prior knee injury or surgery

›Prior ACL reconstruction

›Prior meniscal surgery

›Anticoagulation or bleeding disorder

›Hemarthrosis risk

›Low threshold imaging and follow-up

›Immunosuppression

›Septic arthritis risk

›Recent infection

›Septic arthritis risk

›IVDU

›Septic arthritis risk

Red flags history

›High-risk symptoms

›Fever with swollen knee

›Septic arthritis concern

›Urgent arthrocentesis pathway

›Severe pain unrelieved

›Compartment syndrome concern

›Occult fracture concern

›Numbness or weakness

›Nerve injury concern

›Cold foot or color change

›Vascular injury concern

03Physical Exam/exam86

Inspection and palpation

›Visual and palpation survey

›Effusion

›Patellar ballotment

›Suprapatellar fullness

›Ecchymosis

›Medial bruising

›Lateral bruising

›Deformity

›Patellar maltracking

›Varus or valgus alignment change

›Point tenderness

›Medial joint line

›Lateral joint line

›Patellar tendon

›Quadriceps tendon

›Fibular head

›Tibial plateau

Range of motion and functional tests

›Motion and function

›Active range of motion

›Extension deficit

›Flexion deficit

›Passive range of motion

›Pain endpoint

›Mechanical block

›Straight-leg raise

›Extensor mechanism integrity

›Patellar tendon rupture concern if unable

Ligament and meniscus assessment

›Stability maneuvers

›ACL tests

›Lachman test

›Increased anterior translation

›Soft endpoint

›Anterior drawer

›Increased anterior translation

›Guarding limitation

›Pivot shift

›Apprehension or clunk

›Often not tolerated acutely

›PCL tests

›Posterior drawer

›Increased posterior translation

›Posterior sag sign

›Quadriceps active test

›Anterior shift with quad contraction

›MCL tests

›Valgus stress at 30 degrees

›Medial gapping

›Pain localized to MCL

›Valgus stress at 0 degrees

›Combined injury concern if gapping

›LCL tests

›Varus stress at 30 degrees

›Lateral gapping

›Pain localized to LCL

›Varus stress at 0 degrees

›Combined injury concern if gapping

›Meniscus tests

›Joint line tenderness

›Medial meniscus pattern

›Lateral meniscus pattern

›Thessaly test

›Joint line pain reproduction

›Limited by acute pain

›McMurray test

›Pain or click with rotation

›Limited by guarding

Neurovascular exam

›Distal limb assessment

›Vascular findings

›Pulse symmetry

›Capillary refill

›Neurologic findings

›Peroneal nerve function

›Tibial nerve function

›Compartment assessment

›Tense compartments

›Pain with passive toe motion

PITFALLS

›Common misses

›Knee dislocation with spontaneous reduction

›Normal alignment on arrival

›Vascular injury still possible

›Extensor mechanism rupture mistaken for sprain

›Inability to straight-leg raise

›High-riding patella sign possible

›Septic arthritis mistaken for traumatic effusion

›Fever may be absent early

›Severe pain with limited ROM

04Differential Diagnosis/ddx52

Traumatic internal derangement

›Ligament and meniscus injuries

›MCL sprain or tear (ICD-10 S83.41)

›Medial pain with valgus stress

›Often from valgus mechanism

›LCL sprain or tear (ICD-10 S83.42)

›Lateral pain with varus stress

›Often from varus mechanism

›ACL sprain or tear (ICD-10 S83.51)

›Pop with immediate swelling

›Giving way episodes

›PCL sprain or tear (ICD-10 S83.52)

›Dashboard mechanism

›Posterior sag sign

›Meniscus tear (ICD-10 S83.2)

›Joint line tenderness

›Locking or catching

›Patellar dislocation or subluxation (ICD-10 S83.0)

›Lateral displacement history

›Medial patellofemoral pain

Fracture and osteochondral injury

›Bony injury mimics

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

›Lateral joint line tenderness

›Pain with axial load

›Patellar fracture (ICD-10 S82.0)

›Anterior knee pain

›Direct blow history

›Femoral condyle osteochondral injury

›Hemarthrosis

›Persistent mechanical symptoms

›Segond fracture association

›ACL injury association

›Lateral capsular injury association

Tendon and extensor mechanism injury

›Tendon pathology

›Quadriceps tendon rupture (ICD-10 S76.1)

›Suprapatellar pain

›Inability to extend

›Patellar tendon rupture (ICD-10 S76.0)

›Infrapatellar pain

›Inability to straight-leg raise

Nontraumatic and infectious causes

›Dangerous nontraumatic etiologies

›Septic arthritis (ICD-10 M00.9)

›Fever

›Severe pain with ROM

›Crystal arthritis (ICD-10 M10)

›Acute inflammatory effusion

›History of gout

›Hemarthrosis on anticoagulation

›Large effusion

›Minor trauma history

›DVT with calf swelling

›Posterior pain

›Risk factors for thrombosis

05Laboratory Tests/lt33

Infection and inflammatory evaluation

›Infection labs when febrile or atraumatic effusion

›CBC with differential

›Leukocytosis supportive only

›Normal CBC does not exclude septic arthritis

›CRP

›Elevated supports inflammation

›Normal early CRP possible

›ESR

›Elevated supports inflammation

›Nonspecific

›Blood cultures when sepsis concern

›Before antibiotics when feasible

›Highest yield with bacteremia risk

Hemarthrosis and bleeding risk evaluation

›Bleeding assessment when large effusion and anticoagulation

›INR for warfarin

›Supratherapeutic level supports bleeding risk

›Guides reversal decisions

›Platelet count

›Thrombocytopenia contribution

›Procedure planning for arthrocentesis

Arthrocentesis studies

›Synovial fluid studies when septic arthritis concern (ACEP Level B)

›Cell count with differential

›WBC > 50,000 per microliter supports septic arthritis

›Lower counts possible with early infection

›Gram stain

›Rapid specificity when positive

›Limited sensitivity

›Culture

›Diagnostic gold standard

›Antibiotics before tap decreases yield

›Crystal analysis

›Monosodium urate

›CPPD

06Diagnostic Tests/dt78

Scoring Systems

›Decision rules for radiography

›Ottawa Knee Rule

›Age 55 years or older

›Radiograph indicated if present

›Not validated for children under 18 years

›Isolated patellar tenderness

›Radiograph indicated if present

›Excludes other bony tenderness

›Fibular head tenderness

›Radiograph indicated if present

›Suggests proximal fibula injury

›Inability to flex to 90 degrees

›Radiograph indicated if present

›Pain-limited ROM

›Inability to bear weight 4 steps

›Radiograph indicated if present

›Both immediately and in ED

›Sensitivity high for fracture detection

›Negative rule supports no radiograph

›Use clinical judgment for atypical cases

›Pittsburgh Knee Rule

›Blunt trauma or fall mechanism

›Entry criterion

›Excludes twisting without impact

›Age under 12 years or over 50 years

›Radiograph indicated if present

›Pediatric applicability advantage

›Inability to walk 4 steps

›Radiograph indicated if present

›Both immediately and in ED

MRI

›MRI indications

›Suspected ligament or meniscus tear with persistent symptoms

›Locking or true mechanical block

›Recurrent instability episodes

›Suspected osteochondral injury

›Hemarthrosis with normal radiograph

›Persistent effusion

›Preoperative planning

›Confirm tear pattern

›Evaluate associated injuries

›MRI considerations

›Not first-line for uncomplicated sprain

›Early conservative management preferred

›Reassess at 1 to 2 weeks

›Contraindications

›Non-MRI compatible implanted devices

›Severe claustrophobia without resources

›CT indications

›Suspected tibial plateau fracture with negative or equivocal radiograph

›High-energy mechanism

›Significant effusion

›Complex fracture characterization

›Preoperative planning

›Articular depression assessment

›CT considerations

›Radiation exposure

›Pediatric risk higher

›Use when benefits outweigh risks

›ACR Appropriateness Criteria alignment (Class IIa)

›CT appropriate for occult plateau fracture concern

›MRI alternative when soft tissue priority

Ultrasound (or US)

›Point-of-care ultrasound applications

›Effusion identification

›Suprapatellar recess fluid

›Guides arthrocentesis

›Quadriceps tendon evaluation

›Discontinuity suggests rupture

›Hematoma adjacent to tendon

›Patellar tendon evaluation

›Fiber disruption suggests rupture

›Dynamic assessment helpful

›DVT evaluation when posterior pain and swelling

›Compression ultrasound pathway

›Follow local protocol

›Ultrasound limitations

›Meniscus and cruciate ligaments limited visualization

›MRI preferred for internal derangement

›Clinical exam remains primary

07Disposition/dispo35

Admission and urgent consultation

›Emergency consult triggers

›Neurovascular compromise

›ABI < 0.9

›Diminished pulses after injury

›Suspected knee dislocation

›Vascular imaging pathway

›Ortho and vascular coordination

›Suspected septic arthritis

›Urgent arthrocentesis

›Early IV antibiotics after cultures

›Extensor mechanism rupture

›Inability to straight-leg raise

›Knee immobilization and urgent ortho follow-up

›Compartment syndrome concern

›Emergent surgical evaluation

›Compartment pressure measurement when uncertain

›Fracture requiring stabilization

›Tibial plateau fracture

›Displaced patellar fracture

Discharge criteria and follow-up

›Safe discharge features

›Hemodynamic stability

›No systemic illness signs

›Pain controlled on oral meds

›Fracture excluded when indicated

›Radiographs per rule negative

›High-risk occult fracture addressed

›No neurovascular deficit

›Pulses intact

›Motor and sensory intact

›Ambulation plan

›Crutches training completed

›Weight-bearing instructions clear

›Follow-up arranged

›Sports medicine or orthopedics within 7 to 14 days

›Earlier follow-up for instability or locking

08Treatment/t96

Nonpharmacologic management

›Initial care bundle

›Relative rest for 48 to 72 hours

›Avoid pivoting and cutting

›Maintain gentle motion as tolerated

›Ice protocol

›15 to 20 minutes

›Every 2 to 3 hours in first 48 hours

›Compression

›Elastic wrap

›Avoid excessive tightness

›Elevation

›Above heart level when possible

›Swelling reduction goal

›Bracing and mobility aids

›Hinged knee brace for collateral ligament sprain (Class IIa)

›MCL grade I to II

›Brace for comfort and protection

›Early ROM encouraged

›LCL grade I to II

›Brace protection

›Avoid varus stress

›Knee immobilizer indications

›Suspected extensor mechanism injury

›Severe pain with instability

›Crutches

›Non-weight-bearing for suspected fracture

›Protected weight-bearing for pain-limited gait

›Rehabilitation pathway

›Early range of motion (Class I)

›Avoid prolonged immobilization when stable

›Quadriceps activation emphasis

›Physical therapy referral

›Persistent pain beyond 7 to 10 days

›Instability episodes

Medications

›Analgesics and anti-inflammatory therapy

›Acetaminophen oral

›Adults 650 to 1,000 mg every 6 to 8 hours

›Maximum 3,000 mg per day preferred outpatient

›Lower maximum with liver disease

›Pediatrics 15 mg/kg every 6 hours

›Maximum 60 mg/kg per day

›Maximum 3,000 mg per day absolute

›Ibuprofen oral (Class I)

›Adults 400 mg every 6 to 8 hours

›Maximum 1,200 mg per day OTC

›Higher doses per clinician judgment with GI risk review

›Pediatrics 10 mg/kg every 6 to 8 hours

›Maximum 40 mg/kg per day

›Maximum 600 mg per dose

›Naproxen oral alternative

›Adults 250 to 500 mg twice daily

›Avoid with renal disease

›Avoid late pregnancy

›Topical diclofenac

›Localized pain option

›Lower systemic risk than oral NSAIDs

›Avoid on broken skin

›Opioid short course for severe pain (Class IIb)

›Oxycodone oral 2.5 to 5 mg every 6 hours as needed

›Small quantity only

›Avoid co-prescribing sedatives

›Pediatrics and adolescents 0.05 to 0.1 mg/kg every 6 hours as needed

›Maximum 5 mg per dose

›Caregiver counseling required

›GI protection and contraindications

›NSAID cautions

›History of peptic ulcer disease

›Chronic kidney disease

›Anticoagulation

›Proton pump inhibitor consideration

›High GI risk and NSAID needed

›Shared decision-making

Procedures

›Arthrocentesis

›Diagnostic indications

›Suspected septic arthritis

›Unexplained large effusion

›Therapeutic indications (Class IIa)

›Tense hemarthrosis with severe pain

›Improved exam after decompression

›Technique and safety notes

›Ultrasound guidance when anatomy difficult

›Anticoagulation risk assessment

›Reduction and immobilization

›Patellar dislocation reduction when present (Class I)

›Neurovascular exam pre and post

›Post-reduction radiograph consideration

Escalation and specialty involvement

›Orthopedics or sports medicine referral triggers

›Suspected ACL tear with instability

›Early rehab initiation

›MRI planning when persistent instability

›Locked knee

›Suspected bucket-handle meniscus

›Time-sensitive surgical evaluation

›High-grade collateral injury

›Significant gapping at 0 degrees

›Multiligament injury concern

09Special Populations/sp30

Pregnancy

›Pregnancy considerations

›Imaging strategy

›Radiography acceptable when indicated

›Shielding practices per local protocol

›Medication safety

›Acetaminophen preferred analgesic (Class I)

›Avoid NSAIDs in third trimester (Class III harm)

›DVT risk higher

›Low threshold DVT evaluation with calf swelling

›Compression ultrasound preferred

Geriatric

›Older adult considerations

›Fracture risk higher with low-energy falls

›Lower threshold imaging

›Occult tibial plateau fracture concern

›Anticoagulation prevalence higher

›Hemarthrosis risk

›INR review if on warfarin

›Polypharmacy and fall risk

›Avoid sedating analgesics when possible

›Mobility safety planning

Pediatrics

›Pediatric considerations

›Decision rule selection

›Ottawa Knee Rule not validated for under 18 years

›Pittsburgh Knee Rule includes pediatric applicability

›Growth plate injury risk

›Salter-Harris patterns possible

›Persistent pain despite normal radiograph requires re-evaluation

›Weight-based dosing adherence

›Acetaminophen and ibuprofen per kg dosing

›Opioids only with careful supervision

10Background/b31

Epidemiology

›Frequency and patterns

›Knee sprains common in sports and falls

›MCL common with valgus mechanisms

›ACL common with pivoting sports

›Meniscal injuries common with twisting

›Often combined with ACL injuries

›Mechanical symptoms suggestive

Pathophysiology

›Tissue injury mechanisms

›Ligament sprain grading

›Grade I microscopic tearing

›Grade II partial tear with laxity

›Grade III complete tear with instability

›Hemarthrosis physiology

›Suggests intra-articular injury

›ACL tear and osteochondral injury associations

›Effusion timing concept

›Immediate swelling suggests bleeding

›Delayed swelling suggests synovitis or meniscal injury

Therapeutic Considerations

›Management principles

›Early controlled motion improves outcomes (Class I)

›Reduces stiffness risk

›Supports faster functional recovery

›Immobilization harms when prolonged (Class III harm)

›Quadriceps atrophy

›Joint stiffness

›NSAIDs and acetaminophen as first-line analgesia (Class I)

›Opioids reserved for rescue

›Topical NSAIDs when systemic risk

›Imaging stewardship

›Decision rules reduce unnecessary radiographs (ACEP Level B)

›MRI targeted to persistent symptoms or surgical planning (Class IIa)

11Patient Discharge Instructions/pdi25

copy discharge instructions

›Knee sprain discharge instructions

›Activity and protection

›Rest from pivoting and impact for several days

›Crutches if painful to walk normally

›Brace or wrap as instructed

›Pain and swelling care

›Ice 15 to 20 minutes every 2 to 3 hours for 2 days

›Compression wrap snug not tight

›Elevation above heart when resting

›Medications

›Acetaminophen as directed on label or clinician plan

›Ibuprofen as directed on label if safe for you

›Return to ED now if

›Foot becomes cold, pale, blue, or numb

›New weakness in foot or toes

›Rapidly worsening swelling or pain

›Fever or redness with severe knee pain

›Inability to straighten knee or knee locks

›Unable to bear weight after pain control

›Follow-up

›Sports medicine or orthopedics in 7 to 14 days

›Earlier follow-up if instability or locking

›Expected recovery

›Mild sprain often improves in 1 to 3 weeks

›Persistent swelling or instability needs reassessment

12References/r17

Clinical guidelines and decision rules

›Core references

›Ottawa Knee Rule original validation and subsequent systematic reviews

›High sensitivity for clinically important knee fractures

›Radiography reduction evidence

›Pittsburgh Knee Rule derivation and validation studies

›Pediatric and adult applicability

›Sensitivity and specificity reporting

›ACR Appropriateness Criteria for acute knee trauma imaging

›Radiography first-line when criteria met

›CT and MRI roles for occult injury

Society recommendations and evidence summaries

›Practice guidance

›AAOS and sports medicine guidance on ligament injury management

›Early rehabilitation emphasis

›Surgical referral indications for instability

›ACEP methodology reference for evidence grading

›Level A B C evidence framework

›Applied to decision-rule use and septic arthritis workup

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed June 16, 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.