01Approach to the Critical Patient/attcp53

Immediate priorities

›Limb-threatening injury screen

›Knee dislocation pattern

›Gross deformity or multidirectional instability

›Multiligamentous injury suggests prior dislocation even if spontaneously reduced

›Vascular compromise

›Popliteal artery injury in 10% to 18% of knee dislocations

›Absent or diminished distal pulses

›Expanding popliteal hematoma or bruit

›If pulse deficit or hard signs of ischemia, emergent vascular surgery consultation

›CT angiography of the affected limb

›Time to revascularization under 6 to 8 hours to preserve limb

›Neurologic and compartment screen

›Common peroneal nerve injury

›Foot drop

›Sensory loss over dorsal foot and first web space

›Compartment syndrome

›Pain out of proportion with passive stretch

›Tense, swollen compartment

›If compartment syndrome suspected, emergent orthopedic consultation for fasciotomy

›Compartment pressure within 30 mmHg of diastolic pressure

›Serial neurovascular checks

›Extensor mechanism and open joint screen

›Extensor mechanism disruption

›Inability to perform straight leg raise

›Palpable gap over patellar or quadriceps tendon

›Open joint injury

›Open wound communicating with joint

02History/hx60

Mechanism and presentation

›Injury mechanism

›Noncontact pivoting, cutting, or deceleration

›Accounts for roughly 40% of injuries

›Landing from a jump with dynamic valgus

›Direct contact to planted leg

›Valgus blow with foot fixed

›Higher multiligamentous injury risk

›Cardinal symptoms

›Audible or perceived pop at time of injury

›Up to 100% specificity in some pediatric studies

›Highly suggestive of intra-articular injury

›Rapid effusion within 2 hours

›Indicates hemarthrosis

›Strongly suggests significant intra-articular injury

›Knee giving way or buckling

›Sensation of instability at injury

›Recurrent episodes suggest functional instability

›Inability to continue activity

›Unable to resume sport immediately

Important negatives and clues

›Features lowering ACL probability

›Absence of pop

›Combined negative findings reduce likelihood

›Absence of immediate effusion

›Delayed or minimal swelling

›Ability to continue activity

›Negative LR around 0.08 when combined with negative Lachman and pivot shift

03Physical Exam/exam56

Inspection and general

›Effusion and gait

›Tense hemarthrosis within 2 hours

›Highly suggestive of significant intra-articular pathology

›Lipohemarthrosis suggests occult fracture

›Gait

›Antalgic or inability to bear weight

›Range of motion

›Typically limited by pain and effusion

›Mechanical block suggests displaced meniscal tear

›Neurovascular exam

›Distal pulses

›Dorsalis pedis and posterior tibial

›ABI if asymmetric

›Peroneal nerve function

›Dorsiflexion and eversion strength

›Sensation first web space

›Straight leg raise

›Rules out extensor mechanism disruption

Ligament provocative tests

›ACL-specific maneuvers

›Lachman test

›Sensitivity 76% to 87%, specificity 85% to 97%

›Knee at 30 degrees flexion

›Assess endpoint quality

›Lever sign test

›Sensitivity 79% to 93%, specificity 91% to 92%

›Easiest to perform acutely and relatively pain-free

04Differential Diagnosis/ddx35

Cannot-miss and structural injuries

›Limb-threatening

›Knee dislocation with vascular injury

›ICD-10 S83.106A

›Popliteal artery injury risk 10% to 18%

›Extensor mechanism rupture

›Inability to straight leg raise

›Palpable tendon gap

›Tibial plateau fracture

›ICD-10 S82.101A

›Point tenderness and inability to bear weight

›Periarticular fractures

›Segond fracture

›Lateral tibial avulsion pathognomonic for ACL tear

›Tibial spine avulsion

›More common in skeletally immature patients

Ligament and soft-tissue mimics

›Other ligament injuries

›ACL tear

›ICD-10 S83.511A

›Positive Lachman and lever sign

›PCL tear

›Posterior drawer positive and posterior sag

›Dashboard mechanism

›MCL or LCL sprain

›MCL coexists in 19% to 38% of ACL tears

›Valgus or varus laxity

›Intra-articular and patellar

05Laboratory Tests/lt27

Indications for laboratory testing

›Routine testing

›Not indicated for isolated ACL tear

›Diagnosis is clinical and imaging based

›Avoid unnecessary phlebotomy

›Targeted only when complication suspected

›Septic arthritis concern

›Preoperative workup

›Joint aspiration analysis

›Hemarthrosis

›Confirms significant intra-articular injury

›Bloody aspirate after acute injury

›Lipohemarthrosis

›Fat globules suggest occult intra-articular fracture

›Synovial fluid studies if infection suspected

›Cell count, Gram stain, culture

›Crystal analysis

Perioperative and inflammatory labs

›Preoperative labs when reconstruction planned

›Complete blood count

›Baseline hemoglobin

›Basic metabolic panel

›Renal function for anesthesia planning

›Coagulation studies

›Note anticoagulant use that worsens hemarthrosis

›Inflammatory markers

›ESR and CRP

›Only if septic arthritis or inflammatory arthropathy in differential

06Diagnostic Tests/dt53

Scoring Systems

›Ottawa Knee Rule

›Criteria for radiography

›Age 55 years or older

›Fibular head tenderness

›Isolated patellar tenderness

›Inability to flex to 90 degrees

›Inability to bear weight 4 steps

›Performance

›Pooled sensitivity 98.5% for fracture

›Any positive criterion prompts X-ray

›ACL Injury Score

›History items

›Immediate instability

›Inability to resume activity

›Sensation of dislocation

›Pivoting or contact activity

›Interpretation

›2 or more items gives 95% sensitivity and 88% PPV

›Useful for triage and specialist referral

›KT-1000 arthrometer

›Quantitative translation

›7 mm or more at 133 N is abnormal

›PPV 97% and NPV 88% in pediatric populations

MRI

›MRI without contrast

›Diagnostic gold standard

›Sensitivity 97% and specificity 100% for ACL tear

07Disposition/dispo23

Discharge pathway

›Emergency department discharge

›Isolated ACL tear with stable neurovascular exam

›No fracture requiring operative fixation

›Adequate analgesia and ambulation with aids

›Discharge package

›Knee immobilizer or hinged brace

›Crutches and protected weight-bearing

›Outpatient referral

›Orthopedic or sports medicine within 1 to 2 weeks

›MRI if not obtained in ED

Admission and escalation

›Orthopedic consultation in ED

›Knee dislocation even if reduced

›Serial vascular exams

›Tibial spine avulsion or locked knee

›Operative planning

›Emergent vascular consultation

›Absent or diminished pulses

›ABI below 0.9

›Signs of limb ischemia

›Observation or admission

›Serial vascular monitoring after dislocation

›Compartment syndrome concern

›Associated fractures requiring operative management

08Treatment/t64

Initial ED stabilization

›RICE protocol

›Rest and protected weight-bearing

›Crutches as tolerated

›Ice and compression

›Reduces effusion and pain

›Elevation

›Limb above heart level

›Immobilization and aspiration

›Knee immobilizer or hinged brace

›Comfort and stability

›Bracing alone does not prevent subluxation

›If tense hemarthrosis, aspiration for symptomatic relief

›Aseptic technique

›Send fluid if infection suspected

Analgesia

›First-line agents

›Acetaminophen

›1000 mg PO every 6 hours

›Maximum 4 g per day

›NSAIDs short course

›Ibuprofen 400 to 600 mg PO every 6 to 8 hours

›Do not impair ligament healing

›Avoid in renal impairment or peptic ulcer disease

›Restricted agents

›Opioids sparingly

›Reserve for severe refractory pain

›Short duration only

09Special Populations/sp33

Pregnancy

›Imaging and analgesia adjustments

›Radiography

›Plain films with abdominal shielding when indicated

›MRI without contrast preferred for definitive imaging

›Analgesia

›Acetaminophen first-line

›Avoid NSAIDs in third trimester

›Ligamentous laxity

›Relaxin increases baseline laxity

›Interpret stress tests cautiously

Geriatric

›Older adult considerations

›Lower sport-related incidence

›Falls and degenerative tears more common

›Higher fracture probability per Ottawa rule

›Comorbidity-driven management

›Nonoperative pathway more often appropriate

›Optimize medical comorbidities before surgery

›Osteoarthritis overlap

›Preexisting degenerative change

›Functional goals guide decisions

Pediatrics

›Skeletally immature considerations

›Physeal status

›Open physes affect surgical technique

›Physeal-sparing reconstruction options

›Injury patterns

10Background/b42

Epidemiology

›Incidence and burden

›Over 200,000 ACL injuries annually in the US

›More than 50% of knee injuries

›Peak incidence at 16 to 18 years

›Sex distribution

›Female noncontact rate 2 to 8 times higher

›Sport-specific risk variation

›Concomitant injury rates

›Meniscal tear 20% to 45% lateral

›MCL injury 19% to 38%

Pathophysiology

›Injury mechanics

›Noncontact loading

›Dynamic knee valgus with deceleration

›Quadriceps-dominant anterior tibial translation

›Contact loading

›Valgus blow to fixed leg

›Higher multiligamentous involvement

›Consequences and natural history

›Hemarthrosis

›Vascular ACL disruption causes rapid effusion

›Post-traumatic osteoarthritis

›Occurs with or without surgery

›Secondary meniscal damage

›Chronic instability accelerates joint degeneration

Therapeutic Considerations

›Operative versus nonoperative balance

11Patient Discharge Instructions/pdi19

copy discharge instructions

›Knee injury home care

›Rest, ice, compression, elevation for the first 48 to 72 hours

›Wear the knee brace or immobilizer as directed

›Use crutches and put only as much weight as is comfortable

›Take acetaminophen or ibuprofen as directed for pain

›Follow-up plan

›See orthopedics or sports medicine within 1 to 2 weeks

›Get the MRI scan if your doctor ordered one

›Start physiotherapy when your specialist advises

›Return to ER immediately for

›Increasing swelling, severe pain, or inability to bear weight

›Numbness, tingling, or weakness in the foot or leg

›Cold, pale, or blue foot

›Knee locking or inability to straighten the knee

›Calf swelling, warmth, or tenderness

›Recovery expectations

›Long-term arthritis risk exists with or without surgery

›Prevention exercises lower the risk of reinjury

›Return to sport is based on recovery milestones, not just time

12References/r11

Guidelines and key sources

›Clinical guidelines

›AAOS clinical practice guideline on ACL injury management

›ACR Appropriateness Criteria acute trauma to the knee

›Team physician consensus statements on musculoskeletal injury

›Landmark and diagnostic literature

›NEJM clinical review of ACL tear by Musahl and Karlsson

›Ottawa Knee Rule diagnostic accuracy systematic reviews

›Lever sign and Lachman test diagnostic accuracy studies

›Coding standards

›ICD-10 S83.511A sprain of ACL of right knee

›SNOMED CT tear of anterior cruciate ligament disorder concept

Evidence & Review

Evidence & Review