What is the appropriate physical examination for left knee pain?

Physical Examination for Left Knee Pain

Begin with systematic inspection and palpation, followed by range of motion assessment, then proceed to specific ligamentous and meniscal testing based on the mechanism of injury and clinical presentation. 1

Initial Assessment and Red Flags

Immediately evaluate for critical red flags that require urgent intervention:

• Palpable gap in tendon (suggests complete rupture requiring surgical consultation) 1
• Gross deformity (indicates fracture or dislocation) 1
• Complete inability to bear weight (warrants immediate imaging) 1
• Fever with joint effusion (septic arthritis is an orthopedic emergency requiring urgent aspiration) 1, 2

Systematic Examination Sequence

Visual Inspection

• Assess for swelling, effusion, and ecchymosis to identify acute injury patterns 1
• Look for quadriceps atrophy (suggests chronic pathology) 3
• Observe gait pattern and ability to bear weight 4

Palpation

• Joint line tenderness (medial or lateral) suggests meniscal pathology or osteoarthritis 1, 5
• Patellar tenderness (isolated) may indicate patellar fracture or patellofemoral syndrome 4, 1
• Fibular head tenderness increases fracture probability 4
• Palpate for effusion using the bulge sign or ballottement test 1

Range of Motion Assessment

• Active and passive flexion/extension to identify mechanical blocks 1
• Inability to flex knee to 90 degrees is an Ottawa Knee Rule criterion requiring radiographs 4, 1
• Use the bounce test to assess for mechanical block to full extension (suggests meniscal tear or loose body) 1, 3

Specific Ligamentous Testing

Anterior Cruciate Ligament (ACL)

The Lachman test is the most sensitive (74%) and specific (95%) test for ACL injury and should be your primary assessment tool 1, 6, 7

• Perform with knee at 20-30 degrees flexion, assessing anterior tibial translation 1
• Pivot shift test provides additional confirmation but has lower sensitivity 3, 7

Posterior Cruciate Ligament (PCL)

• Posterior drawer test is highly sensitive and specific for PCL tears 6
• Tibial sag test (Godfrey sign) enhances diagnostic accuracy 3, 7

Collateral Ligaments

• Valgus stress testing (at 0° and 30° flexion) evaluates medial collateral ligament 3
• Varus stress testing (at 0° and 30° flexion) evaluates lateral collateral ligament 3

Meniscal Testing

Combine at least two meniscal tests to increase diagnostic accuracy 7

• McMurray test is highly specific but has low sensitivity for meniscal tears 6, 7
• Apley grind test provides additional diagnostic information 3, 7
• Thessaly test (performed with patient standing) has good diagnostic performance 7
• Joint line tenderness has good sensitivity but poor specificity 6

Critical Examination Pitfalls

Re-examine patients after 3-5 days if initial assessment is limited by excessive swelling and pain, as examination accuracy is significantly reduced for up to 48 hours after acute injury 1

Do not apply clinical decision rules in these situations:

• Gross deformity present 1
• Penetrating injury 1
• Prosthetic hardware in place 1
• Multiple injuries 1
• Altered mental status 1
• Peripheral neuropathy 1

Special Population Considerations

In adolescents with knee pain and inability to bear weight, always examine the hip and consider slipped capital femoral epiphysis (SCFE), as hip pathology commonly presents as knee pain 1

Ottawa Knee Rule Application

Apply the Ottawa Knee Rule to determine imaging necessity in patients ≥18 years with acute trauma 4, 1

Radiographs are indicated if ANY of the following:

• Age ≥55 years 4, 1
• Isolated patellar tenderness 4
• Fibular head tenderness 4
• Inability to flex knee to 90° 4, 1
• Inability to bear weight immediately after injury 4, 1
• Inability to take 4 weight-bearing steps in the emergency department 4, 1

Examination for Chronic Knee Pain

For patients >40 years with usage-related pain and short morning stiffness, focus on:

• Joint line tenderness (particularly medial, reflecting typical OA pattern) 5
• Bony enlargement at joint margins 5
• Coarse crepitus (present in 81% of OA patients vs 36% pain-free individuals) 5
• Reduced passive range of motion compared to contralateral knee 5

Imaging is not required for diagnosis in typical OA presentations 5