What is the initial workup for knee pain?

Initial Workup for Knee Pain

Radiography is the initial imaging study recommended for evaluating chronic knee pain, with a minimum of two views (anteroposterior and lateral) of the affected knee. 1

Clinical Evaluation Components

History - Focus on:

• Age (patients >55 years have higher risk of fracture and osteoarthritis)
• Location, onset, duration, and quality of pain
• Mechanical symptoms (locking, catching, giving way)
• History of trauma or injury
• Swelling patterns
• Previous knee problems or surgeries
• Associated systemic symptoms

Physical Examination - Systematic approach:

• Inspection for deformity, swelling, erythema
• Palpation for tenderness, effusion, warmth
• Range of motion assessment
• Strength testing
• Neurovascular evaluation
• Special tests:
  • McMurray test (specific but not sensitive for meniscal tears) 2
  • Lachman test (more sensitive and specific than drawer sign for ACL tears) 2
  • Assessment of joint line tenderness (sensitive but not specific for meniscal tears) 2

Imaging Algorithm

1. Initial Imaging: Plain Radiographs

   • Should include at least one frontal projection (anteroposterior, Rosenberg, or tunnel view), a tangential patellar view, and a lateral view 1
   • Provides quick, cost-effective identification of fractures, degenerative changes, osteochondral defects, and effusions 3
   • Reserve for chronic knee pain (>6 weeks) or acute traumatic pain meeting specific criteria 4

2. When Initial Radiographs Are Normal or Show Joint Effusion:

   • MRI without contrast is usually the appropriate next step if symptoms persist 1
   • MRI has near 100% sensitivity for fracture detection and excellent capability for detecting bone marrow contusions, occult fractures, and soft tissue injuries 5

3. When Trauma Is Present - Ottawa Knee Rules: Consider radiographs if any of the following are present:

   • Age >55 years
   • Tenderness at head of fibula or patella
   • Inability to bear weight for 4 steps
   • Inability to flex knee to 90 degrees 2

Special Considerations

When to Consider Alternative Imaging:

• CT Scanning: When better delineation of fractures is needed or when MRI is contraindicated 5, 3
• MRI: When soft tissue injuries (meniscal, ligamentous) are suspected and surgery is being contemplated 3
• Radiography of Hip or Lumbar Spine: When knee radiographs are unremarkable and there is clinical concern for referred pain 1

Red Flags Requiring Urgent Evaluation:

• Severe pain, swelling, and instability after acute trauma
• Inability to bear weight
• Signs of joint infection (fever, erythema, limited range of motion) 4

Common Pitfalls to Avoid

1. Premature MRI: Approximately 20% of patients with chronic knee pain have MRI without recent radiographs, which may be unnecessary 1

2. Missing Referred Pain: Knee pain may originate from hip or lumbar spine pathology, requiring appropriate imaging of these areas when knee radiographs are normal 1

3. Overreliance on Imaging: Clinical features (age >50 years, morning stiffness <30 minutes, crepitus, bony enlargement) are 89% sensitive and 88% specific for underlying chronic arthritis, often making additional imaging unnecessary 2

4. Failure to Apply Ottawa Knee Rules: These evidence-based criteria help determine when radiographs are necessary for suspected fractures, avoiding unnecessary imaging 2