Initial Workup for Knee Pain

History and Physical Examination Components

The American College of Radiology recommends evaluating for focal tenderness, effusion, and weight-bearing ability, which are key criteria in the Ottawa rules for determining the need for imaging, especially in patients with acute trauma or chronic pain 1, 2
Documenting the presence of gross deformity, palpable mass, penetrating injury, prosthetic hardware, or altered mental status is crucial, as these conditions warrant immediate radiographic evaluation regardless of other findings 1, 2

For acute knee trauma, the American College of Radiology suggests that radiographs should be the initial imaging modality when one or more Ottawa rule criteria are present, with a minimum of two radiographic views (anteroposterior and lateral) obtained 1, 2, 3
Additional views, such as cross-table lateral, patellofemoral, and internal and external oblique views, may be necessary for comprehensive evaluation 1, 2
For chronic knee pain, radiographs should include at least one frontal projection, a tangential patellar view, and a lateral view, and consider radiographs of the hip or lumbar spine if knee radiographs are unremarkable and referred pain is suspected 4, 5, 6

MRI is not routinely used as the initial imaging study for acute knee trauma but should be considered when initial radiographs are normal but pain persists, surgery is being contemplated, or evaluation of soft tissue structures is needed 4, 6, 7
CT may be appropriate as the next imaging study when radiographically occult fractures are suspected or detailed evaluation of patellofemoral anatomy is needed for chronic pain related to subluxation or maltracking 1, 2, 9

Avoid ordering MRI without recent radiographs, which occurs in approximately 20% of patients with chronic knee pain, and be aware that meniscal tears are often incidental findings in older patients 4, 5, 10
Clinical judgment should supersede clinical guidelines in specific cases, and ultrasound can be useful for detecting synovial pathology but is not routinely used as the initial imaging study for knee pain 1, 2

For patients with suspected fracture but normal radiographs, CT has shown 100% sensitivity in detecting tibial plateau fractures compared to 83% with radiographs 9
In chronic knee pain with normal radiographs, MRI can detect bone marrow lesions, which are associated with increased pain, especially in males or patients with a family history of osteoarthritis 7