Imaging Workup for Chronic Bilateral Knee Pain in Young Adults

Initial Radiographic Assessment

The American College of Radiology recommends obtaining bilateral knee radiographs—including at least one frontal view (AP, Rosenberg, or tunnel), a tangential patellar view, and a lateral view—as the first‑line imaging study for any patient with chronic knee pain, regardless of clinical suspicion. 1
Approximately 20 % of patients with chronic knee pain receive MRI without having recent radiographs, representing an inappropriate use of advanced imaging. 2

If radiographs are normal or show only a joint effusion and pain persists after conservative therapy, the ACR advises proceeding to non‑contrast MRI of both knees. 3
MRI is more sensitive than plain radiography and can detect patellofemoral cartilage abnormalities and bone‑marrow lesions that are linked to anterior knee pain in younger patients. 4
MRI also identifies meniscal tears, synovitis, joint effusions, and popliteal (Baker) cysts, providing a comprehensive evaluation of intra‑articular pathology. 5
Additional soft‑tissue and overuse conditions visible on MRI include patellar tendinopathy, fat‑pad impingement (Hoffa’s disease), iliotibial band syndrome, medial plicae, and discoid meniscus. 3
Rare but clinically important pathologies such as intra‑articular tumors, ganglion cysts, pigmented villonodular synovitis, and osteonecrosis are also detectable on MRI. 3

When knee radiographs are unremarkable, the ACR recommends hip radiographs to rule out referred pain from hip pathology. 6
Lumbar spine imaging should be considered if clinical features suggest radicular involvement (e.g., leg numbness or weakness). 6

In cases of bilateral knee pain with systemic features (e.g., prolonged morning stiffness), plain radiographs remain the initial imaging modality. 7
MRI or musculoskeletal ultrasound can be added to detect early synovitis and erosions before radiographic changes become apparent. 7

Computed tomography without IV contrast is indicated when patellofemoral maltracking or subluxation is suspected, to assess trochlear morphology and the tibial tubercle‑trochlear groove distance. 8
Musculoskeletal ultrasound is useful for confirming joint effusions and guiding aspiration, as well as for evaluating popliteal cysts, medial plicae, and vastus medialis oblique dysfunction in patellofemoral pain. 4

The ACR cautions against ordering MRI without a recent (within the past year) set of knee radiographs, as this leads to unnecessary testing and increased cost. 2
Meniscal tears identified on MRI may represent incidental findings, especially in older patients; their clinical relevance is lower in an 18‑year‑old. 1

When bilateral knee pain is accompanied by systemic signs suggestive of inflammatory arthritis, laboratory evaluation—including rheumatoid factor, anti‑CCP, ESR, CRP, and ANA—should be pursued to complement imaging findings. 7

The American College of Radiology (ACR) recommends that bilateral standing knee radiographs (anteroposterior, lateral, and tangential patellar views) be obtained as the mandatory first imaging study for any patient with medial knee pain; subsequent non‑contrast MRI is reserved for cases where radiographs are normal or show only effusion and symptoms persist after conservative therapy【9】.
The ACR specifies that the radiographic series should include at least one frontal projection (AP, Rosenberg, or tunnel view), a tangential patellar view, and a lateral view of the symptomatic knee【9】.
Approximately 20 % of patients receive MRI without a recent (within the past year) radiographic series, representing unnecessary advanced imaging and increased health‑care cost【9】.

When plain radiographs are unremarkable or reveal only effusion, the ACR advises proceeding to non‑contrast MRI of both knees if pain continues despite conservative management【9】.

The ACR recommends hip radiographs when knee films are normal and clinical findings suggest a hip origin for the referred medial knee pain【9】.
Lumbar spine imaging is indicated when the patient reports radicular symptoms such as leg numbness or weakness, to assess for possible referred pain【9】.

CT without IV contrast is reserved for suspected patellofemoral maltracking or subluxation, allowing assessment of trochlear morphology and tibial‑tubercle‑trochlear‑groove distance【10】.

The ACR cautions against over‑interpreting meniscal tears on MRI in older adults, as many are incidental findings that do not require surgical intervention【10】.
In patients over 70 years, bilateral structural abnormalities on MRI may be present even when symptoms are unilateral, limiting the ability to differentiate painful from non‑painful knees【10】.
Bone scintigraphy should not be used routinely because of low specificity and inferior anatomic resolution compared with CT or MRI, although it may be useful for localizing pain in selected cases【10】.

Never order MRI without recent radiographs—this practice leads to unnecessary testing and higher costs【9】.