What is the recommended approach for a comprehensive knee exam in patients presenting with knee pain or injury, considering age, medical history, and potential underlying conditions such as osteoarthritis?

Comprehensive Knee Examination Approach

Initial Clinical Assessment Strategy

Begin with a structured history focusing on age-specific red flags, mechanism of injury, and functional limitations to determine imaging necessity and urgency of referral. 1, 2

Critical History Elements to Obtain

• Age and timing: Document patient age (critical thresholds: <12,18-55, >55 years), onset (acute vs. chronic >6 weeks), and whether trauma occurred 1, 3, 4
• Pain characteristics: Location (anterior, medial, lateral, posterior), quality, duration, and presence of morning stiffness (<30 minutes suggests OA; ≥60 minutes suggests inflammatory arthritis) 3, 5
• Mechanical symptoms: Locking, catching, giving way, or inability to bear weight 3, 4
• Constitutional symptoms: Fever, erythema, warmth (suggests infection requiring urgent evaluation) 2, 4
• Functional impact: Ability to walk 4 steps, climb stairs, rise from chairs 1, 5

Systematic Physical Examination Components

Always examine the uninjured knee first for comparison, then assess the hip and lumbar spine to exclude referred pain. 6, 1, 7

Inspection and Palpation

• Joint effusion: Presence suggests intra-articular pathology requiring further evaluation 1
• Focal tenderness: Palpate fibular head, patella, joint lines, tibial tubercle, and popliteal fossa 1, 3, 6
• Soft tissue changes: Erythema, warmth, swelling (red flags for infection or inflammatory arthritis) 2, 5

Range of Motion and Stability Testing

• Flexion assessment: Inability to flex to 90° is an Ottawa rule criterion requiring radiographs 1
• Collateral ligaments: Valgus stress (medial collateral) and varus stress (lateral collateral) testing 6
• Anterior cruciate ligament: Lachman test (74% sensitive, 95% specific—superior to drawer sign) 8, 6
• Posterior cruciate ligament: Posterior drawer and tibial sag tests (81% sensitive, 95% specific) 8, 6

Meniscal Evaluation

• Joint line tenderness: 75-83% sensitive but only 27-83% specific for meniscal tears 3, 8
• McMurray test: Knee rotation with extension (52-61% sensitive, 84-97% specific) 3, 8, 6
• Bounce test and Apley grind test: Additional confirmatory maneuvers 6

Patellofemoral Assessment

• Anterior knee pain with squat: 91% sensitive, 50% specific for patellofemoral pain syndrome 3
• Patellar tenderness and tracking: Assess for isolated patellar tenderness (Ottawa criterion) and maltracking 1

Essential Additional Examinations

• Hip range of motion: Internal/external rotation and impingement testing to exclude referred pain 1, 7
• Lumbar spine: Straight leg raise and neurologic examination if knee radiographs unremarkable 1, 7
• Gait assessment: Observe ability to bear weight and walk 4 steps 1, 2
• Neurovascular status: Document distal pulses and sensation 4

Age-Specific Diagnostic Considerations

Pediatric Patients (5-18 years)

• Osgood-Schlatter disease: Tibial tubercle tenderness in active adolescents 1, 2
• Sinding-Larsen-Johansson syndrome: Inferior patellar pole pain 1, 2
• Osteochondritis dissecans: Consider in persistent pain despite conservative treatment 1
• Juvenile idiopathic arthritis: Bilateral symptoms with constitutional signs 2

Adults (18-45 years)

• Patellofemoral pain: Lifetime prevalence 25%, anterior pain with squatting 3
• Traumatic meniscal tears: Twisting injury mechanism in younger active patients 3
• Ligamentous injuries: Acute trauma with instability or inability to bear weight 8, 6

Older Adults (≥45 years)

• Osteoarthritis: Most likely diagnosis with activity-related pain, <30 minutes morning stiffness, age >50, crepitus, bony enlargement (95% sensitive, 69% specific for age >45; 89% sensitive, 88% specific with clinical criteria) 3, 8
• Degenerative meniscal tears: Often asymptomatic; majority of patients >70 have meniscal tears on imaging 1, 5, 3
• Popliteal cysts: Posterior knee pain or swelling 7

Imaging Decision Algorithm

Acute Trauma (<6 weeks)

Apply Ottawa Knee Rules to determine radiograph necessity (100% sensitivity for fractures with 35% reduction in unnecessary imaging): 1

Obtain knee radiographs if ANY of the following:

• Age ≥55 years
• Isolated patellar tenderness
• Fibular head tenderness
• Inability to flex knee to 90°
• Inability to bear weight immediately after injury
• Inability to walk 4 steps in examination room

Alternative: Pittsburgh Rule requires radiographs for age <12 or >50 years plus inability to take 4 weight-bearing steps. 1

Chronic Pain (≥6 weeks)

Radiographs are the mandatory initial imaging study for all patients ≥5 years with chronic knee pain. 1

Required views: frontal projection (AP, Rosenberg, or tunnel), lateral, and tangential patellar 1

Post-Radiograph Algorithm

If radiographs normal or show only joint effusion with persistent pain: MRI without IV contrast is the next appropriate study. 1

If radiographs show degenerative changes or chondrocalcinosis: Consider MRI without contrast, knee aspiration (for suspected crystal arthropathy or infection), or CT without contrast depending on clinical context 1

If radiographs show OCD, loose bodies, or prior cartilage/meniscal repair: MRI without IV contrast is indicated. 1

If radiographs show prior osseous injury (Segond fracture, tibial spine avulsion): MRI without IV contrast to evaluate associated soft tissue injuries. 1

Critical Pitfalls to Avoid

• Never order MRI without recent radiographs (within past year)—approximately 20% of chronic knee pain patients receive premature MRI 1
• Do not attribute all symptoms to knee pathology without examining hip and lumbar spine—referred pain is common when knee radiographs are unremarkable 1, 7
• Recognize that meniscal tears are often incidental findings—asymptomatic tears are present in the majority of patients >70 years 1, 5
• Do not overlook red flags requiring urgent evaluation: fever, erythema, warmth, severe pain with inability to bear weight, or acute trauma with significant effusion 2, 4
• Avoid imaging children without red flags—most pediatric bilateral knee pain is self-limiting and benign 2
• Do not rush to surgery for degenerative meniscal tears—exercise therapy is first-line even with mechanical symptoms 3

Initial Management Based on Examination Findings

No Red Flags Present

Initiate conservative treatment for 4-6 weeks before considering advanced imaging: 2, 3

• Activity modification and load management
• Physical therapy emphasizing strengthening exercises (hip and knee for patellofemoral pain; quadriceps for OA)
• Weight loss if BMI elevated (critical for knee OA)
• NSAIDs and ice application
• Patient education and self-management programs

Red Flags Present

Immediate radiographs or specialist referral indicated for: 1, 2, 4

• Acute trauma meeting Ottawa criteria
• Signs of infection (fever, erythema, warmth, severe effusion)
• Inability to bear weight or walk 4 steps
• Suspected fracture or dislocation
• Neurovascular compromise