What is the recommended initial X-ray (X-ray) for a patient presenting with knee pain?

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Recommended X-ray Views for Knee Pain

For initial evaluation of knee pain, obtain a minimum three-view series: anteroposterior (AP), lateral (at 25-30 degrees of flexion), and tangential patellar view. 1

Standard Initial Radiographic Protocol

Knee radiographs should include at least one frontal projection (AP, Rosenberg, or tunnel view), a tangential patellar view, and a lateral view of the affected knee. 2

Essential Views:

  • Anteroposterior (AP) view: Essential for evaluating the tibiofemoral joint, fractures, and alignment 1
  • Lateral view: Must be obtained with the knee at 25-30 degrees of flexion in the lateral decubitus position, demonstrating the patella in profile 1
    • This view allows evaluation for joint effusion and, when obtained as a cross-table lateral with horizontal beam, can visualize lipohemarthrosis (indicating intra-articular fracture) 1
  • Tangential patellar view (sunrise/skyline): Completes the standard three-view series to evaluate the patellofemoral joint 1

Context-Specific Modifications

For Acute Trauma:

  • Minimum two views required: AP and lateral (with knee at 25-30 degrees flexion) 2, 1
  • Add patellofemoral view when patellar fracture, subluxation, or dislocation is suspected 2, 1
  • Internal and external oblique views are commonly performed as supplemental projections in acute knee trauma 1

For Chronic Knee Pain or Suspected Osteoarthritis:

  • Weight-bearing views significantly improve diagnostic accuracy 1
  • Recommended series: Weight-bearing AP (or tunnel view) + lateral + tangential patellar view 1
  • The combination of weight-bearing AP and tunnel view significantly increases detection of joint space narrowing in both lateral and medial compartments compared to AP alone 3
  • The tunnel view provides additional information on affected compartments not visible on AP imaging alone 3

When to Order Radiographs

Ottawa Knee Rules (Strongest Evidence):

Order radiographs if ANY of the following are present: 1, 4

  • Age >55 years
  • Isolated tenderness of the patella
  • Tenderness at the head of the fibula
  • Inability to flex knee to 90 degrees
  • Inability to bear weight both immediately after injury and in the emergency department

Clinical Judgment Supersedes Rules:

Never apply decision rules in patients with: 1

  • Gross deformity
  • Palpable mass
  • Penetrating injury
  • Prosthetic hardware
  • Unreliable examination due to altered mental status (head injury, drug/alcohol use, dementia)
  • Neuropathy (paraplegia, diabetes)
  • History suggesting increased risk of fracture

Critical Pitfalls to Avoid

Never skip radiographs even when effusion is clinically obvious, as plain films are essential to rule out fractures, prosthetic complications, or chronic changes before proceeding to advanced imaging 1

Do not order MRI without recent radiographs first—approximately 20% of patients with chronic knee pain inappropriately receive MRI without radiographs within the prior year 2, 1

Consider referred pain: In patients with chronic knee pain, if knee radiographs are unremarkable, consider hip or lumbar spine radiographs if there is clinical evidence or concern for pathology in those regions 2

Practical Algorithm by Clinical Scenario

Acute Trauma with Positive Ottawa Criteria:

  • AP + lateral (25-30° flexion) + consider patellofemoral view 1

Chronic Knee Pain (Initial Evaluation):

  • Weight-bearing AP (or tunnel view) + lateral + tangential patellar view 1

Suspected Patellar Pathology:

  • Standard views + dedicated patellofemoral/skyline view 1

Suspected Arthritis:

  • Weight-bearing AP + weight-bearing tunnel view + lateral + tangential patellar 1

Next Steps After Initial Radiographs

If radiographs are normal or show only joint effusion but pain persists, the next indicated examination is usually MRI without IV contrast, which is more sensitive than radiography for detecting meniscal tears, ligamentous injuries, bone marrow lesions, and cartilage abnormalities 2

CT without IV contrast may be indicated to evaluate patellofemoral anatomy in chronic pain related to repetitive patellofemoral subluxation or maltracking, or to better characterize fractures 2

References

1
Guideline

Recommended X-ray Views for Knee Pain

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

2
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

4
Research

Evaluation of acute knee pain in primary care.

Annals of internal medicine, 2003

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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