What is the initial evaluation and management approach for a patient presenting with knee pain?

Initial Evaluation and Management of Knee Pain

Begin with plain radiographs of the knee (minimum two views: anteroposterior and lateral) for all patients ≥5 years old presenting with knee pain, whether acute or chronic. 1, 2

History: Key Elements to Document

• Age and onset pattern: Patients <40 years with anterior knee pain during squatting suggest patellofemoral pain (91% sensitive), while patients ≥45 years with activity-related pain and <30 minutes of morning stiffness suggest osteoarthritis (95% sensitive) 3

• Mechanical symptoms: Document locking, catching, or giving way, which may indicate meniscal pathology (joint line tenderness 83% sensitive and specific; McMurray test 61% sensitive, 84% specific) 3

• Red flags requiring urgent evaluation: Fever with joint swelling/erythema (septic arthritis), gross deformity, palpable mass, penetrating injury, inability to bear weight with severe pain/swelling after trauma 1, 2, 4

• Weight-bearing ability and range of motion: Critical for applying Ottawa Knee Rules in acute trauma 1, 2

Physical Examination: Systematic Approach

• Inspection: Assess for effusion, erythema, deformity, and muscle atrophy 4

• Palpation: Check for focal tenderness over fibular head, isolated patellar tenderness, joint line tenderness, and warmth 1, 2

• Range of motion testing: Document ability to flex knee to 90° (Ottawa criteria) and presence of crepitus 1, 4

• Provocative maneuvers: Perform McMurray test for meniscal tears, patellar apprehension test for instability, and assess for ligamentous laxity 4, 3

• Neurovascular examination: Essential to exclude referred pain from hip or spine pathology 4

Imaging Algorithm

For Acute Trauma (Use Ottawa Knee Rules)

Order radiographs if ANY of the following criteria are met: 1, 2

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

Additional views beyond standard AP/lateral: Consider cross-table lateral, patellofemoral (sunrise), and oblique views for comprehensive evaluation 2

For Chronic Knee Pain (>6 weeks)

• Initial radiographs should include: Frontal projection, tangential patellar view, and lateral view 1, 2

• If radiographs are normal or show only effusion: MRI without contrast is usually appropriate as the next step to evaluate soft tissue structures, menisci, ligaments, and bone marrow lesions 1, 2

• If radiographs show degenerative changes: MRI may be appropriate only when symptoms are not explained by radiographic findings or when stress fractures are suspected 1

• Consider hip or lumbar spine radiographs: If knee radiographs are unremarkable and referred pain is suspected 2

Common Pitfalls to Avoid

• Do not order MRI without recent radiographs first: This occurs inappropriately in ~20% of chronic knee pain cases 2

• Recognize incidental findings: Meniscal tears are frequently present in asymptomatic older patients and may not be the pain source 2, 3

• Avoid unnecessary imaging in acute trauma: Applying Ottawa rules can reduce radiographs by 23-35% while maintaining 100% sensitivity for fractures 1

When to Consider Advanced Imaging

• CT without contrast: Appropriate when radiographically occult fractures are suspected (100% sensitive for tibial plateau fractures vs 83% for radiographs) or for detailed patellofemoral anatomy evaluation 1, 2

• Ultrasound: Useful for confirming effusions, guiding aspiration, detecting Baker cysts, and evaluating superficial structures, but not as a comprehensive screening tool 1, 2

• Joint aspiration: Indicated when infection or crystal disease is suspected, can be ultrasound or fluoroscopy-guided 1

Initial Management Based on Diagnosis

Osteoarthritis (Most Common in ≥45 Years)

• First-line treatment: Exercise therapy, weight loss if overweight, education, and self-management programs 3
• Avoid: Routine MRI in typical OA cases unless symptoms unexplained by radiographs 1

Patellofemoral Pain (Common in <40 Years, Active Patients)

• First-line treatment: Hip and knee strengthening exercises combined with foot orthoses or patellar taping 3
• No indication for surgery 3

Meniscal Tears

• Conservative management first: Exercise therapy for 4-6 weeks, even with mechanical symptoms in degenerative tears 3
• Surgery only for: Severe traumatic bucket-handle tears with displaced tissue 3

Urgent Referral Criteria

Immediate orthopedic consultation required for: 2, 4

• Suspected septic arthritis (fever, severe swelling, erythema, limited ROM)
• Severe pain with instability and inability to bear weight after acute trauma
• Gross deformity or neurovascular compromise
• Locked knee that cannot be extended