What is the recommended approach for a knee physical assessment in a patient presenting with knee pain or limited mobility, regardless of age or medical history, including previous knee injuries, surgeries, or conditions such as osteoarthritis?

Knee Physical Assessment

A comprehensive knee physical assessment should use a biopsychosocial approach that systematically evaluates physical status (including pain, joint alignment, mobility, strength, proprioception), activities of daily living, participation in work/leisure, mood, and patient education needs, with the examination always beginning on the uninjured knee for comparison. 1

Initial Assessment Components

The EULAR guidelines recommend the following structured evaluation 1:

Physical Status Assessment

• Pain characteristics: Location, intensity, duration, and aggravating/relieving factors 1
• Fatigue and sleep quality: Impact on overall function 1
• Lower limb joint status: Comprehensive evaluation of foot, knee, and hip 1
• Mobility assessment: Gait pattern, range of motion (active and passive), and functional limitations 1, 2
• Strength testing: Quadriceps, hamstrings, and hip musculature 1
• Joint alignment: Varus or valgus deformity, which commonly develops with osteoarthritis severity 3
• Proprioception and posture: Balance and joint position sense 1
• Comorbidities and weight: Essential for treatment planning 1

Functional and Psychosocial Assessment

• Activities of daily living: Specific limitations in stairs, rising from chairs, walking distance 1, 4
• Participation: Impact on work, education, leisure activities, and social roles 1
• Mood assessment: Depression and anxiety commonly accompany chronic knee pain 1
• Health beliefs and motivation: Patient's understanding and readiness for self-management 1

Systematic Physical Examination Technique

Inspection and Palpation

• Always examine the uninjured knee first for comparison 2
• Joint line palpation: Tenderness is 83% sensitive and 83% specific for meniscal tears 5
• Patellar tenderness: Isolated patellar tenderness suggests patellofemoral pathology 6
• Fibular head tenderness: May indicate lateral collateral ligament injury or fracture 6
• Effusion assessment: Presence suggests inflammation, trauma, or underlying pathology 1, 3
• Crepitus: Common in patellofemoral compartment osteoarthritis but often asymptomatic in elderly 4, 3

Range of Motion Testing

• Active and passive flexion/extension: Normal knee flexion is approximately 135 degrees 2
• Inability to flex to 90 degrees: Red flag requiring radiographic evaluation in acute trauma 6
• Limited range of motion: Common finding in osteoarthritis 3

Ligamentous Stability Testing

Collateral Ligaments 2:

• Valgus stress test: Assesses medial collateral ligament (MCL) integrity
• Varus stress test: Evaluates lateral collateral ligament (LCL)

Cruciate Ligaments 2, 7:

• Lachman test: Most sensitive and specific test for anterior cruciate ligament (ACL) tears (74% sensitive, 95% specific) 7
• Anterior drawer test: Less sensitive than Lachman for ACL evaluation 7
• Posterior drawer test: Evaluates posterior cruciate ligament (PCL) - 81% sensitive, 95% specific 7
• Pivot shift test: Assesses ACL integrity and rotational instability 2

Meniscal Testing

McMurray Test 2, 5, 7:

• Concurrent knee rotation (internal for lateral meniscus, external for medial meniscus) with extension
• 97% specific but only 52% sensitive for meniscal tears 7
• 61% sensitive and 84% specific when performed correctly 5

Joint Line Tenderness 5, 7:

• 75-83% sensitive but only 27% specific for meniscal tears
• High sensitivity makes it useful for screening but poor specificity limits diagnostic value

Apley's Grind Test 2:

• Patient prone with knee flexed to 90 degrees
• Compression with rotation to stress menisci

Special Considerations by Age and Presentation

For Suspected Osteoarthritis (Age ≥45 years) 1, 5:

• Clinical criteria alone are highly accurate: age >50 years, morning stiffness <30 minutes, crepitus, or bony enlargement (89% sensitive, 88% specific) 7
• Weight-bearing radiographs confirm diagnosis but clinical features are sufficient for initial management 1, 3

For Patellofemoral Pain (Typically <40 years) 5:

• Anterior knee pain during squat: 91% sensitive, 50% specific 5
• Patellar tracking assessment and apprehension test
• Hip and knee strength evaluation essential 5

For Elderly Patients with Crepitus 4:

• Focus on functional limitations and pain rather than crepitus alone - the American College of Radiology emphasizes that crepitus is often incidental 4
• Meniscal tears are present in the majority of people over 70 years and are frequently asymptomatic 1, 4
• Consider referred pain from hip or lumbar spine if knee examination is unremarkable 1, 4

Functional Performance Testing

For younger patients with ACL or meniscal injury, functional performance tests complement the physical examination 1:

• Single Leg Hop Test: Sufficient reliability, construct validity, and responsiveness (high to moderate quality evidence) 1
• Crossover Hop Test: Sufficient reliability and construct validity (moderate quality evidence) 1

Critical Pitfalls to Avoid

Do Not Overlook Red Flags 6:

• Gross deformity, palpable mass, or penetrating injury require immediate imaging regardless of clinical decision rules 6
• Inability to bear weight (4 steps) in acute trauma mandates radiography 6
• Multiple injuries, altered mental status, or neuropathy make examination unreliable 6

Avoid Imaging Overuse 1, 4, 5:

• Approximately 20% of patients with chronic knee pain undergo MRI without recent radiographs - this is often premature 1
• In elderly patients, do not overreact to crepitus or incidental meniscal tears on imaging without correlating to symptoms 4
• For osteoarthritis, clinical diagnosis is sufficient - adding plain films improves sensitivity only slightly without improving specificity 7

Consider Alternative Pain Sources 1, 4:

• Hip pathology can present as knee pain - examine hip if knee radiographs are unremarkable 1
• Lumbar spine pathology may cause referred knee pain 1

Integration with Treatment Planning

The assessment should directly inform individualized management 1:

• Tailor treatment based on risk factors (obesity, mechanical factors, physical activity), general factors (age, comorbidity), pain intensity, signs of inflammation, and structural damage severity 1
• Non-pharmacological interventions (education, exercise, weight loss, assistive devices) should be core components for all patients 1
• Functional limitations guide rehabilitation progression and treatment success evaluation 1