Knee PainAPPROACH

MUSCULOSKELETAL AND EXTREMITIES · 19 SECTIONS

⚲

578 items

☷ Legend

⚲

Resuscitation and Universal Approaches9▾

Chest and Cardiovascular12▾

Respiratory11▾

Abdominal and Gastrointestinal24▾

Renal and Urinary7▾

Neurologic11▾

Back and Neck8▾

Women's Health, Pregnancy, and GU11▾

Infectious Disease and Fever Syndromes11▾

Allergy and Dermatology7▾

Musculoskeletal and Extremities14▾

Shoulder Pain Elbow Pain Wrist Pain Hand Pain Hip Pain Knee Pain Ankle Pain Foot Pain Cast Or Splint Complication Symptoms Wound Check And Suture Related Visits Joint Swelling And Monoarthritis Suspected Septic Joint Presentation Suspected Tendon Rupture Presentation Limp Or Refusal To Bear Weight

Trauma and Wounds14▾

ENT, Eye, Dental10▾

Endocrine, Metabolic, and Abnormal Labs9▾

Toxicology and Behavioral14▾

Pediatrics16▾

Environmental and Exposure4▾

01History/hx66

HPI

›Knee pain context

›Traumatic

›Mechanism

›Audible pop

›Immediate swelling

›Able to continue activity

›Atraumatic

›Recent infection

›Recent new exercise

›Prior joint disease

›Time course

›Sudden

›Gradual

›Intermittent

OPQRST

›Onset

›Exact start time

›Sudden versus gradual

›Provocation and palliation

›Worse with weight bearing

›Worse with stairs

›Worse with kneeling

›Worse with twisting

›Relief with rest

›Relief with ice

›Quality

›Sharp

›Aching

›Catching

›Locking

›Region and radiation

›Anterior

›Medial

›Lateral

›Posterior

›Radiation to calf

›Radiation to hip

›Severity

›Pain score 0 to 10

›Weight bearing limitation

›Timing

›Constant

›With activity

›Night pain

Associated symptoms

›Local symptoms

›Swelling

›Warmth

›Erythema

›Instability

›Mechanical locking

›Giving way

›Systemic symptoms

›Fever

›Chills

›Malaise

›Neurovascular symptoms

›Numbness

›Weakness

›Cold foot

Prior episodes and baseline

›Baseline function

›Usual walking distance

›Usual stairs tolerance

›Prior similar episodes

›Prior imaging

›Prior injections

›Prior surgery

›Prior physical therapy

02Alarm Features/alarm30

Immediate threats

›Limb and life threats

›Suspected septic arthritis

›Fever

›Hot swollen joint

›Severe pain with passive range of motion

›Knee dislocation concern

›Gross deformity

›Popliteal pulse abnormal

›Peroneal nerve deficit

›Open fracture

›Wound near joint

›Visible bone

›Compartment syndrome

›Pain out of proportion

›Pain with passive stretch

›Paresthesia

›DVT concern

›Calf swelling

›Calf tenderness

›Unilateral edema

Vital sign danger thresholds

›High risk vitals

›Systolic blood pressure less than 90 mmHg

›Heart rate 120 or more

›Temperature 38.0 C or more

›Oxygen saturation less than 92 percent

Escalation triggers

›Immediate escalation

›Rapidly progressive pain and swelling

›Neurovascular compromise

›Inability to bear weight after high energy trauma

›Immunocompromised with monoarthritis

03Medications/meds27

Current and recent medications

›Medication exposure relevant to knee pain

›Anticoagulants

›Warfarin

›Apixaban

›Rivaroxaban

›Dabigatran

›Antiplatelets

›Clopidogrel

›Aspirin

›Immunosuppressants

›Chronic steroids

›Biologic agents

›Recent antibiotics

›Within 30 days

›Incomplete course

Analgesic history

›Pain treatment already tried

›Acetaminophen dose and timing

›NSAID dose and timing

›Topical NSAID use

›Opioid exposure

Contraindications to common therapies

›NSAID risk

›CKD

›GI bleed history

›Anticoagulant use

›Acetaminophen risk

›Liver disease

›Heavy alcohol use

04Diet/diet10

Hydration and exposures

›Intake pattern

›Poor oral intake

›Dehydration symptoms

›Alcohol exposure

›Binge within 72 hours

›Daily use

›Purine related pattern

›High meat intake

›Shellfish intake

›Sugary beverages

05Review of Systems/ros21

Musculoskeletal

›Joint pattern

›Monoarticular

›Oligoarticular

›Polyarticular

›Morning stiffness more than 30 minutes

›Other joint symptoms

›Back pain

›Hip pain

›Ankle pain

Infectious and inflammatory

›Infection symptoms

›Fever

›Chills

›Recent skin infection

›Inflammatory clues

›Rash

›Eye pain

›Oral ulcers

Cardiopulmonary and thromboembolic

›Thrombosis symptoms

›Dyspnea

›Pleuritic chest pain

›Hemoptysis

06Collateral History and Family History/chafh14

Collateral and reliability

›Source

›Parent or guardian

›Caregiver

›EMS

›Facility staff

›Reliability factors

›Intoxication

›Dementia

›Language barrier

Family history

›Heritable and early disease

›Early osteoarthritis

›Inflammatory arthritis

›Thrombophilia

›Bleeding disorders

07Risk Factors/rf18

Infection risk

›Septic arthritis risks

›Diabetes mellitus (E11.9)

›Chronic kidney disease (N18.9)

›Immunosuppression

›Prior joint surgery

›Prosthetic joint

›IVDU

Trauma and overuse risk

›Mechanical risks

›Pivoting sports

›Occupational kneeling

›Recent increase in training load

Thrombosis and bleeding risk

›DVT risks

›Recent immobilization

›Recent surgery

›Active cancer (C80.1)

›Hemarthrosis risks

›Anticoagulation

›Bleeding disorder

08Differential Diagnosis/ddx67

Life threatening

›Cannot miss

›Septic arthritis (M00.9)

›Severe pain with passive range of motion

›Fever or systemic illness

›Immunocompromised

›Knee dislocation with popliteal artery injury

›Absent or asymmetric pulses

›ABI less than 0.9

›Tibial plateau fracture (S82.14)

›High energy mechanism

›Large effusion

›Necrotizing soft tissue infection

›Pain out of proportion

›Rapid progression

›DVT (I82.409)

›Unilateral calf swelling

›Risk factors present

Common

›High prevalence

›Osteoarthritis (M17.9)

›Age over 50

›Activity related pain

›Morning stiffness short

›Meniscal tear (S83.2)

›Twisting injury

›Joint line tenderness

›Locking or catching

›ACL injury (S83.51)

›Pivot injury

›Immediate swelling

›Instability

›MCL or LCL sprain (S83.41)

›Valgus or varus injury

›Medial or lateral tenderness

›Patellofemoral pain syndrome (M22.2)

›Anterior pain

›Worse with stairs

›Prepatellar bursitis (M70.4)

›Kneeling exposure

›Localized superficial swelling

›Gout (M10.9)

›Sudden severe pain

›Prior flares

›CPPD pseudogout (M11.20)

›Older age

›Acute effusion

Less common

›Lower prevalence and mimics

›Baker cyst rupture

›Posterior knee fullness

›Calf pain and swelling

›Iliotibial band syndrome (M76.3)

›Lateral pain with running

›Tenderness over lateral femoral condyle

›Quadriceps or patellar tendinopathy (M76.5)

›Pain with jumping

›Tenderness at tendon

›Hemarthrosis

›Anticoagulation

›Bleeding disorder

›Inflammatory arthritis

›Multiple joints

›Morning stiffness prolonged

›Referred pain from hip

›Limited hip range of motion

›Groin pain

›Malignancy

›Night pain

›Weight loss

09Past Medical History/pmh27

Relevant conditions

›Chronic disease and relevance

›Osteoarthritis (M17.9)

›Affected side

›Prior imaging findings

›Rheumatoid arthritis (M06.9)

›Current DMARDs

›Flare pattern

›Diabetes mellitus (E11.9)

›Recent A1C trend

›Foot ulcer history

›CKD (N18.9)

›Baseline creatinine

›Dialysis

›Gout (M10.9)

›Prior crystal proven diagnosis

›Urate lowering therapy

Surgeries and devices

›Prior procedures

›Knee arthroscopy

›ACL reconstruction

›Total knee arthroplasty

›Recent intraarticular injection

Baseline function and supports

›Functional baseline

›Ambulatory aid use

›Falls history

›Social supports

›Ability to obtain follow up

›Home assistance

10Physical Exam/exam57

General and vitals

›Global assessment

›Toxic appearance

›Fever

›Hemodynamic stability

›Gait and function

›Able to bear weight

›Antalgic gait

Knee inspection and palpation

›Local findings

›Effusion

›Erythema

›Warmth

›Ecchymosis

›Wound or puncture

›Bony tenderness

Range of motion

›Motion pattern

›Active range limited

›Passive range limited

›Pain with passive range of motion

›Extension lag

Ligament exam

›Stability tests

›ACL

›Lachman

›Anterior drawer

›PCL

›Posterior drawer

›Posterior sag sign

›MCL

›Valgus stress

›Pain versus laxity

›LCL

›Varus stress

›Pain versus laxity

Meniscus and patellofemoral

›Mechanical tests

›Joint line tenderness

›McMurray

›Thessaly

›Patellar tracking and pain

›Patellar apprehension

›Patellar grind

Extensor mechanism

›Quadriceps and patellar tendon integrity

›Straight leg raise

›Palpable tendon defect

Neurovascular and adjacent joints

›Distal perfusion and nerves

›Dorsalis pedis pulse

›Posterior tibial pulse

›Capillary refill

›Peroneal nerve sensation

›Peroneal nerve motor

›Hip and ankle screen

›Hip range of motion

›Ankle tenderness

Special populations pitfalls

›High risk groups

›Prosthetic joint pain

›Immunocompromised

›Anticoagulated

›Pediatric

›Pregnancy

11Lab Studies/labs27

Core labs when infection or systemic illness

›Infection evaluation

›CBC

›Leukocytosis supportive only

›Normal does not exclude septic arthritis

›CRP

›Trend helpful

›Elevated supports infection or inflammation

›ESR

›Subacute infection support

›Baseline elevated in chronic disease

›Blood cultures

›Fever

›Hemodynamic instability

Arthrocentesis studies for effusion with concern for infection or crystals

›Synovial fluid panel

›WBC count with differential

›Gram stain

›Culture

›Crystal analysis

›Glucose

›Protein

Coagulation and bleeding evaluation

›Hemarthrosis risk

›INR for warfarin

›Platelet count

›aPTT if indicated

Metabolic and medication safety

›Analgesic safety checks

›Creatinine for NSAID risk

›ALT for acetaminophen risk

12Imaging/img45

Scoring Systems

›Knee radiography decision tools

›Ottawa Knee Rule

›Age 55 or older

›Isolated patella tenderness

›Fibular head tenderness

›Unable to flex to 90 degrees

›Unable to bear weight 4 steps

›Pittsburgh Knee Rule

›Blunt trauma or fall

›Age under 12

›Age 50 or older

›Unable to walk 4 weight bearing steps

MRI

›MRI knee use cases

›Suspected internal derangement with persistent symptoms

›Suspected meniscus tear with mechanical symptoms

›Suspected ligament tear with instability

›Occult fracture concern with normal radiographs

›Tibial plateau occult fracture

›Stress fracture

›Infection extension assessment

›Osteomyelitis concern

›Deep abscess concern

›Contraindications and limits

›Non compatible implanted device

›Availability and timing local protocol dependent

›CT knee use cases

›Complex fracture definition

›Tibial plateau fracture characterization

›Preoperative planning

›Vascular injury assessment when indicated

›CTA lower extremity for dislocation concern

›Contrast nephropathy risk

›Radiation considerations

›Pediatric minimize exposure

›Pregnancy local protocol dependent

Ultrasound

›Ultrasound applications

›POCUS for effusion

›Suprapatellar recess fluid

›Guidance for arthrocentesis

›DVT evaluation pathway

›Compression ultrasound when Wells suggests

›Negative study may require repeat based on risk

›Baker cyst assessment

›Cyst visualization

›Rupture pattern support

13Special Tests/spec22

Bedside maneuvers and procedures

›Targeted diagnostics

›Arthrocentesis

›Indications

›Acute atraumatic effusion

›Concern for septic arthritis

›Concern for crystals

›Pitfalls

›Antibiotics before culture reduces yield

›Crystal disease can coexist with infection

›ABI for dislocation concern

›ABI less than 0.9 suggests vascular injury

›Normal ABI does not fully exclude intimal injury

›Serial neurovascular exams

›Recheck pulses after reduction or splinting

›Recheck peroneal nerve function

Procedural imaging adjuncts

›Guidance tools

›Ultrasound guided aspiration

›Improves success in small effusions

›Avoids vascular structures

›Joint fluid gross appearance

›Purulent supports infection

›Frank blood supports hemarthrosis

14ECG/ecg7

When ECG is relevant in knee pain presentations

›Fall or collapse context

›Syncope preceding injury

›Palpitations preceding fall

›High risk comorbidity context

›Chest pain

›Dyspnea

›Electrolyte abnormality concern

15Assessment/ax22

Problem framing

›Knee pain syndrome classification

›Traumatic with deformity

›Fracture or dislocation until proven otherwise

›Neurovascular status drives urgency

›Traumatic without deformity

›Internal derangement consideration

›Occult fracture consideration

›Atraumatic hot swollen knee

›Septic arthritis versus crystal disease

›Cellulitis mimic

›Chronic progressive pain

›Osteoarthritis pattern

›Overuse pattern

Severity and risk stratification

›High risk features

›Fever or systemic illness

›Severe pain with passive range of motion

›Inability to bear weight

›Neurovascular compromise

›Complications to exclude

›Vascular injury

›Compartment syndrome

›Sepsis

16Plan/plan56

First 5 minutes for critical presentations

›Immediate workflow

›Continuous monitoring

›Cardiac monitor if unstable

›Pulse oximetry

›IV access criteria

›Suspected sepsis

›High energy trauma

›Analgesia early

›IV opioid if severe pain and instability excluded

›Avoid delaying reduction for imaging when dislocation obvious

›Time critical tests

›X ray for suspected fracture

›ABI for suspected dislocation

›Arthrocentesis for suspected septic arthritis

Analgesia and symptom control

›Multimodal pain plan

›Acetaminophen PO

›1000 mg every 6 to 8 hours

›Maximum 3000 mg per day typical

›Ibuprofen PO

›400 mg every 6 to 8 hours

›Avoid in CKD

›Avoid in GI bleed history

›Naproxen PO

›500 mg once then 250 mg every 6 to 8 hours

›Avoid in pregnancy third trimester

›Topical diclofenac gel

›Apply to knee up to 4 times daily

›Avoid on broken skin

›Opioid for severe pain

›Oxycodone PO 5 mg every 6 hours as needed

›Avoid with sedatives

Diagnostic sequencing

›Pathway driven testing

›Trauma pathway

›Apply Ottawa Knee Rule for radiographs

›Consider CT for tibial plateau fracture

›Atraumatic effusion pathway

›Arthrocentesis before antibiotics when stable

›Blood cultures if febrile

›DVT pathway

›Wells assessment local protocol dependent

›Compression ultrasound when indicated

Infection management

›Suspected septic arthritis

›Ortho consultation early

›Drainage plan

›OR washout consideration

›Antibiotics after cultures when feasible

›Vancomycin IV local protocol dependent

›Add gram negative coverage when risk factors present

Immobilization and mobility

›Function protection

›Knee immobilizer for instability or extensor mechanism concern

›Crutches for protected weight bearing

›Avoid prolonged immobilization for simple sprain

Reassessment loop

›Timed reassessment

›Pain and function recheck within 30 to 60 minutes after analgesia

›Neurovascular recheck after splinting

›Recheck temperature and hemodynamics if infection concern

17Disposition/dispo21

ICU and high acuity triggers

›ICU or resuscitation level care

›Sepsis with hypotension

›Rapidly progressive soft tissue infection

›Vascular compromise with instability

Inpatient admission indications

›Admit criteria

›Suspected septic arthritis

›Open fracture

›Neurovascular injury

›Uncontrolled pain despite ED therapy

›Unable to ambulate safely

Observation pathway

›Observation appropriate

›Pain control and mobility training needed

›Indeterminate imaging requiring repeat evaluation

Discharge criteria and follow up

›Discharge appropriate

›Neurovascularly intact

›Pain controlled with oral regimen

›Safe mobility with aid

›Clear follow up plan

›Follow up timing

›Sports medicine or orthopedics within 3 to 7 days for suspected internal derangement

›Primary care within 1 to 2 weeks for degenerative patterns

18Discharge Instructions/di25

Copy discharge instructions

›Knee pain discharge summary

›Today you were seen for knee pain

›Your exam did not show signs of an emergency problem at this time

›Some injuries do not show up on early imaging

›Medications

›Acetaminophen as directed on the label

›Ibuprofen or naproxen if safe for you

›Do not take more than one NSAID at the same time

›Avoid NSAIDs if kidney disease or stomach bleeding history

›Activity

›Rest and avoid painful activities for 48 hours

›Ice 15 to 20 minutes up to 4 times daily

›Elevate the leg when resting

›Use crutches if weight bearing is painful

›Follow up

›Arrange follow up within 3 to 7 days if pain or swelling persists

›Earlier follow up if you have instability or locking

›Return to the emergency department now for

›Fever

›Increasing redness or warmth

›Rapidly increasing swelling

›Inability to walk

›New numbness or weakness

›Cold foot or worsening color change

›Chest pain or shortness of breath

19References/r16

Core guidelines and decision tools

›Evidence base

›Ottawa Knee Rule validation studies

›Clinical decision tool for knee radiography after acute injury

›Use within appropriate population

›IDSA guidelines for septic arthritis management

›Antibiotics and source control principles

›Local protocol dependent regimens

›AAOS clinical practice guidance for knee osteoarthritis

›Nonoperative symptom management

›Shared decision making for imaging

›ACR Appropriateness Criteria for acute knee pain imaging

›Modality selection by suspected pathology

›Radiation and contrast considerations

›ACCP antithrombotic guidance for suspected DVT pathways

›Pretest probability use

›Imaging sequencing local protocol dependent

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed February 24, 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.

Knee PainAPPROACH

MUSCULOSKELETAL AND EXTREMITIES · 19 SECTIONS

⚲

578 items

☷ Legend

⚲

Resuscitation and Universal Approaches9▾

Chest and Cardiovascular12▾

Respiratory11▾

Abdominal and Gastrointestinal24▾

Renal and Urinary7▾

Neurologic11▾

Back and Neck8▾

Women's Health, Pregnancy, and GU11▾

Infectious Disease and Fever Syndromes11▾

Allergy and Dermatology7▾

Musculoskeletal and Extremities14▾

Trauma and Wounds14▾

ENT, Eye, Dental10▾

Endocrine, Metabolic, and Abnormal Labs9▾

Toxicology and Behavioral14▾

Pediatrics16▾

Environmental and Exposure4▾

01History/hx66

HPI

›Knee pain context

›Traumatic

›Mechanism

›Audible pop

›Immediate swelling

›Able to continue activity

›Atraumatic

›Recent infection

›Recent new exercise

›Prior joint disease

›Time course

›Sudden

›Gradual

›Intermittent

OPQRST

›Onset

›Exact start time

›Sudden versus gradual

›Provocation and palliation

›Worse with weight bearing

›Worse with stairs

›Worse with kneeling

›Worse with twisting

›Relief with rest

›Relief with ice

›Quality

›Sharp

›Aching

›Catching

›Locking

›Region and radiation

›Anterior

›Medial

›Lateral

›Posterior

›Radiation to calf

›Radiation to hip

›Severity

›Pain score 0 to 10

›Weight bearing limitation

›Timing

›Constant

›With activity

›Night pain

Associated symptoms

›Local symptoms

›Swelling

›Warmth

›Erythema

›Instability

›Mechanical locking

›Giving way

›Systemic symptoms

›Fever

›Chills

›Malaise

›Neurovascular symptoms

›Numbness

›Weakness

›Cold foot

Prior episodes and baseline

›Baseline function

›Usual walking distance

›Usual stairs tolerance

›Prior similar episodes

›Prior imaging

›Prior injections

›Prior surgery

›Prior physical therapy

02Alarm Features/alarm30

Immediate threats

›Limb and life threats

›Suspected septic arthritis

›Fever

›Hot swollen joint

›Severe pain with passive range of motion

›Knee dislocation concern

›Gross deformity

›Popliteal pulse abnormal

›Peroneal nerve deficit

›Open fracture

›Wound near joint

›Visible bone

›Compartment syndrome

›Pain out of proportion

›Pain with passive stretch

›Paresthesia

›DVT concern

›Calf swelling

›Calf tenderness

›Unilateral edema

Vital sign danger thresholds

›High risk vitals

›Systolic blood pressure less than 90 mmHg

›Heart rate 120 or more

›Temperature 38.0 C or more

›Oxygen saturation less than 92 percent

Escalation triggers

›Immediate escalation

›Rapidly progressive pain and swelling

›Neurovascular compromise

›Inability to bear weight after high energy trauma

›Immunocompromised with monoarthritis

03Medications/meds27

Current and recent medications

›Medication exposure relevant to knee pain

›Anticoagulants

›Warfarin

›Apixaban

›Rivaroxaban

›Dabigatran

›Antiplatelets

›Clopidogrel

›Aspirin

›Immunosuppressants

›Chronic steroids

›Biologic agents

›Recent antibiotics

›Within 30 days

›Incomplete course

Analgesic history

›Pain treatment already tried

›Acetaminophen dose and timing

›NSAID dose and timing

›Topical NSAID use

›Opioid exposure

Contraindications to common therapies

›NSAID risk

›CKD

›GI bleed history

›Anticoagulant use

›Acetaminophen risk

›Liver disease

›Heavy alcohol use

04Diet/diet10

Hydration and exposures

›Intake pattern

›Poor oral intake

›Dehydration symptoms

›Alcohol exposure

›Binge within 72 hours

›Daily use

›Purine related pattern

›High meat intake

›Shellfish intake

›Sugary beverages

05Review of Systems/ros21

Musculoskeletal

›Joint pattern

›Monoarticular

›Oligoarticular

›Polyarticular

›Morning stiffness more than 30 minutes

›Other joint symptoms

›Back pain

›Hip pain

›Ankle pain

Infectious and inflammatory

›Infection symptoms

›Fever

›Chills

›Recent skin infection

›Inflammatory clues

›Rash

›Eye pain

›Oral ulcers

Cardiopulmonary and thromboembolic

›Thrombosis symptoms

›Dyspnea

›Pleuritic chest pain

›Hemoptysis

06Collateral History and Family History/chafh14

Collateral and reliability

›Source

›Parent or guardian

›Caregiver

›EMS

›Facility staff

›Reliability factors

›Intoxication

›Dementia

›Language barrier

Family history

›Heritable and early disease

›Early osteoarthritis

›Inflammatory arthritis

›Thrombophilia

›Bleeding disorders

07Risk Factors/rf18

Infection risk

›Septic arthritis risks

›Diabetes mellitus (E11.9)

›Chronic kidney disease (N18.9)

›Immunosuppression

›Prior joint surgery

›Prosthetic joint

›IVDU

Trauma and overuse risk

›Mechanical risks

›Pivoting sports

›Occupational kneeling

›Recent increase in training load

Thrombosis and bleeding risk

›DVT risks

›Recent immobilization

›Recent surgery

›Active cancer (C80.1)

›Hemarthrosis risks

›Anticoagulation

›Bleeding disorder

08Differential Diagnosis/ddx67

Life threatening

›Cannot miss

›Septic arthritis (M00.9)

›Severe pain with passive range of motion

›Fever or systemic illness

›Immunocompromised

›Knee dislocation with popliteal artery injury

›Absent or asymmetric pulses

›ABI less than 0.9

›Tibial plateau fracture (S82.14)

›High energy mechanism

›Large effusion

›Necrotizing soft tissue infection

›Pain out of proportion

›Rapid progression

›DVT (I82.409)

›Unilateral calf swelling

›Risk factors present

Common

›High prevalence

›Osteoarthritis (M17.9)

›Age over 50

›Activity related pain

›Morning stiffness short

›Meniscal tear (S83.2)

›Twisting injury

›Joint line tenderness

›Locking or catching

›ACL injury (S83.51)

›Pivot injury

›Immediate swelling

›Instability

›MCL or LCL sprain (S83.41)

›Valgus or varus injury

›Medial or lateral tenderness

›Patellofemoral pain syndrome (M22.2)

›Anterior pain

›Worse with stairs

›Prepatellar bursitis (M70.4)

›Kneeling exposure

›Localized superficial swelling

›Gout (M10.9)

›Sudden severe pain

›Prior flares

›CPPD pseudogout (M11.20)

›Older age

›Acute effusion

Less common

›Lower prevalence and mimics

›Baker cyst rupture

›Posterior knee fullness

›Calf pain and swelling

›Iliotibial band syndrome (M76.3)

›Lateral pain with running

›Tenderness over lateral femoral condyle

›Quadriceps or patellar tendinopathy (M76.5)

›Pain with jumping

›Tenderness at tendon

›Hemarthrosis

›Anticoagulation

›Bleeding disorder

›Inflammatory arthritis

›Multiple joints

›Morning stiffness prolonged

›Referred pain from hip

›Limited hip range of motion

›Groin pain

›Malignancy

›Night pain

›Weight loss

09Past Medical History/pmh27

Relevant conditions

›Chronic disease and relevance

›Osteoarthritis (M17.9)

›Affected side

›Prior imaging findings

›Rheumatoid arthritis (M06.9)

›Current DMARDs

›Flare pattern

›Diabetes mellitus (E11.9)

›Recent A1C trend

›Foot ulcer history

›CKD (N18.9)

›Baseline creatinine

›Dialysis

›Gout (M10.9)

›Prior crystal proven diagnosis

›Urate lowering therapy

Surgeries and devices

›Prior procedures

›Knee arthroscopy

›ACL reconstruction

›Total knee arthroplasty

›Recent intraarticular injection

Baseline function and supports

›Functional baseline

›Ambulatory aid use

›Falls history

›Social supports

›Ability to obtain follow up

›Home assistance

10Physical Exam/exam57

General and vitals

›Global assessment

›Toxic appearance

›Fever

›Hemodynamic stability

›Gait and function

›Able to bear weight

›Antalgic gait

Knee inspection and palpation

›Local findings

›Effusion

›Erythema

›Warmth

›Ecchymosis

›Wound or puncture

›Bony tenderness

Range of motion

›Motion pattern

›Active range limited

›Passive range limited

›Pain with passive range of motion

›Extension lag

Ligament exam

›Stability tests

›ACL

›Lachman

›Anterior drawer

›PCL

›Posterior drawer

›Posterior sag sign

›MCL

›Valgus stress

›Pain versus laxity

›LCL

›Varus stress

›Pain versus laxity

Meniscus and patellofemoral

›Mechanical tests

›Joint line tenderness

›McMurray

›Thessaly

›Patellar tracking and pain

›Patellar apprehension

›Patellar grind

Extensor mechanism

›Quadriceps and patellar tendon integrity

›Straight leg raise

›Palpable tendon defect

Neurovascular and adjacent joints

›Distal perfusion and nerves

›Dorsalis pedis pulse

›Posterior tibial pulse

›Capillary refill

›Peroneal nerve sensation

›Peroneal nerve motor

›Hip and ankle screen

›Hip range of motion

›Ankle tenderness

Special populations pitfalls

›High risk groups

›Prosthetic joint pain

›Immunocompromised

›Anticoagulated

›Pediatric

›Pregnancy

11Lab Studies/labs27

Core labs when infection or systemic illness

›Infection evaluation

›CBC

›Leukocytosis supportive only

›Normal does not exclude septic arthritis

›CRP

›Trend helpful

›Elevated supports infection or inflammation

›ESR

›Subacute infection support

›Baseline elevated in chronic disease

›Blood cultures

›Fever

›Hemodynamic instability

Arthrocentesis studies for effusion with concern for infection or crystals

›Synovial fluid panel

›WBC count with differential

›Gram stain

›Culture

›Crystal analysis

›Glucose

›Protein

Coagulation and bleeding evaluation

›Hemarthrosis risk

›INR for warfarin

›Platelet count

›aPTT if indicated

Metabolic and medication safety

›Analgesic safety checks

›Creatinine for NSAID risk

›ALT for acetaminophen risk

12Imaging/img45

Scoring Systems

›Knee radiography decision tools

›Ottawa Knee Rule

›Age 55 or older

›Isolated patella tenderness

›Fibular head tenderness

›Unable to flex to 90 degrees

›Unable to bear weight 4 steps

›Pittsburgh Knee Rule

›Blunt trauma or fall

›Age under 12

›Age 50 or older

›Unable to walk 4 weight bearing steps

MRI

›MRI knee use cases

›Suspected internal derangement with persistent symptoms

›Suspected meniscus tear with mechanical symptoms

›Suspected ligament tear with instability

›Occult fracture concern with normal radiographs

›Tibial plateau occult fracture

›Stress fracture

›Infection extension assessment

›Osteomyelitis concern

›Deep abscess concern

›Contraindications and limits

›Non compatible implanted device

›Availability and timing local protocol dependent

›CT knee use cases

›Complex fracture definition

›Tibial plateau fracture characterization

›Preoperative planning

›Vascular injury assessment when indicated

›CTA lower extremity for dislocation concern

›Contrast nephropathy risk

›Radiation considerations

›Pediatric minimize exposure

›Pregnancy local protocol dependent

Ultrasound

›Ultrasound applications

›POCUS for effusion

›Suprapatellar recess fluid

›Guidance for arthrocentesis

›DVT evaluation pathway

›Compression ultrasound when Wells suggests

›Negative study may require repeat based on risk

›Baker cyst assessment

›Cyst visualization

›Rupture pattern support

13Special Tests/spec22

Bedside maneuvers and procedures

›Targeted diagnostics

›Arthrocentesis

›Indications

›Acute atraumatic effusion

›Concern for septic arthritis

›Concern for crystals

›Pitfalls

›Antibiotics before culture reduces yield

›Crystal disease can coexist with infection

›ABI for dislocation concern

›ABI less than 0.9 suggests vascular injury

›Normal ABI does not fully exclude intimal injury

›Serial neurovascular exams

›Recheck pulses after reduction or splinting

›Recheck peroneal nerve function

Procedural imaging adjuncts

›Guidance tools

›Ultrasound guided aspiration

›Improves success in small effusions

›Avoids vascular structures

›Joint fluid gross appearance

›Purulent supports infection

›Frank blood supports hemarthrosis

14ECG/ecg7

When ECG is relevant in knee pain presentations

›Fall or collapse context

›Syncope preceding injury

›Palpitations preceding fall

›High risk comorbidity context

›Chest pain

›Dyspnea

›Electrolyte abnormality concern

15Assessment/ax22

Problem framing

›Knee pain syndrome classification

›Traumatic with deformity

›Fracture or dislocation until proven otherwise

›Neurovascular status drives urgency

›Traumatic without deformity

›Internal derangement consideration

›Occult fracture consideration

›Atraumatic hot swollen knee

›Septic arthritis versus crystal disease

›Cellulitis mimic

›Chronic progressive pain

›Osteoarthritis pattern

›Overuse pattern

Severity and risk stratification

›High risk features

›Fever or systemic illness

›Severe pain with passive range of motion

›Inability to bear weight

›Neurovascular compromise

›Complications to exclude

›Vascular injury

›Compartment syndrome

›Sepsis

16Plan/plan56

First 5 minutes for critical presentations

›Immediate workflow

›Continuous monitoring

›Cardiac monitor if unstable

›Pulse oximetry

›IV access criteria

›Suspected sepsis

›High energy trauma

›Analgesia early

›IV opioid if severe pain and instability excluded

›Avoid delaying reduction for imaging when dislocation obvious

›Time critical tests

›X ray for suspected fracture

›ABI for suspected dislocation

›Arthrocentesis for suspected septic arthritis

Analgesia and symptom control

›Multimodal pain plan

›Acetaminophen PO

›1000 mg every 6 to 8 hours

›Maximum 3000 mg per day typical

›Ibuprofen PO

›400 mg every 6 to 8 hours

›Avoid in CKD

›Avoid in GI bleed history

›Naproxen PO

›500 mg once then 250 mg every 6 to 8 hours

›Avoid in pregnancy third trimester

›Topical diclofenac gel

›Apply to knee up to 4 times daily

›Avoid on broken skin

›Opioid for severe pain

›Oxycodone PO 5 mg every 6 hours as needed

›Avoid with sedatives

Diagnostic sequencing

›Pathway driven testing

›Trauma pathway

›Apply Ottawa Knee Rule for radiographs

›Consider CT for tibial plateau fracture

›Atraumatic effusion pathway

›Arthrocentesis before antibiotics when stable

›Blood cultures if febrile

›DVT pathway

›Wells assessment local protocol dependent

›Compression ultrasound when indicated

Infection management

›Suspected septic arthritis

›Ortho consultation early

›Drainage plan

›OR washout consideration

›Antibiotics after cultures when feasible

›Vancomycin IV local protocol dependent

›Add gram negative coverage when risk factors present

Immobilization and mobility

›Function protection

›Knee immobilizer for instability or extensor mechanism concern

›Crutches for protected weight bearing

›Avoid prolonged immobilization for simple sprain

Reassessment loop

›Timed reassessment

›Pain and function recheck within 30 to 60 minutes after analgesia

›Neurovascular recheck after splinting

›Recheck temperature and hemodynamics if infection concern

17Disposition/dispo21

ICU and high acuity triggers

›ICU or resuscitation level care

›Sepsis with hypotension

›Rapidly progressive soft tissue infection

›Vascular compromise with instability

Inpatient admission indications

›Admit criteria

›Suspected septic arthritis

›Open fracture

›Neurovascular injury

›Uncontrolled pain despite ED therapy

›Unable to ambulate safely

Observation pathway

›Observation appropriate

›Pain control and mobility training needed

›Indeterminate imaging requiring repeat evaluation

Discharge criteria and follow up

›Discharge appropriate

›Neurovascularly intact

›Pain controlled with oral regimen

›Safe mobility with aid

›Clear follow up plan

›Follow up timing

›Sports medicine or orthopedics within 3 to 7 days for suspected internal derangement

›Primary care within 1 to 2 weeks for degenerative patterns

18Discharge Instructions/di25

Copy discharge instructions

›Knee pain discharge summary

›Today you were seen for knee pain

›Your exam did not show signs of an emergency problem at this time

›Some injuries do not show up on early imaging

›Medications

›Acetaminophen as directed on the label

›Ibuprofen or naproxen if safe for you

›Do not take more than one NSAID at the same time

›Avoid NSAIDs if kidney disease or stomach bleeding history

›Activity

›Rest and avoid painful activities for 48 hours

›Ice 15 to 20 minutes up to 4 times daily

›Elevate the leg when resting

›Use crutches if weight bearing is painful

›Follow up

›Arrange follow up within 3 to 7 days if pain or swelling persists

›Earlier follow up if you have instability or locking

›Return to the emergency department now for

›Fever

›Increasing redness or warmth

›Rapidly increasing swelling

›Inability to walk

›New numbness or weakness

›Cold foot or worsening color change

›Chest pain or shortness of breath

19References/r16

Core guidelines and decision tools

›Evidence base

›Ottawa Knee Rule validation studies

›Clinical decision tool for knee radiography after acute injury

›Use within appropriate population

›IDSA guidelines for septic arthritis management

›Antibiotics and source control principles

›Local protocol dependent regimens

›AAOS clinical practice guidance for knee osteoarthritis

›Nonoperative symptom management

›Shared decision making for imaging

›ACR Appropriateness Criteria for acute knee pain imaging

›Modality selection by suspected pathology

›Radiation and contrast considerations

›ACCP antithrombotic guidance for suspected DVT pathways

›Pretest probability use

›Imaging sequencing local protocol dependent

Evidence & Review

Reviewed by SymptomDx Medical Team · Last reviewed February 24, 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.