Diagnosis and Management of Medial Knee Pain

Clinical Presentation and Diagnosis

The American College of Radiology recommends that patients with medial knee pain and popping sensation but negative x-ray should proceed directly to MRI for definitive diagnosis, as the majority (93.5%) of patients presenting with acute knee injuries have soft-tissue injuries rather than osseous injuries 1
Medial meniscal tear is a likely diagnosis, as the medial meniscus is more vulnerable to injury due to its intimate attachment to the medial collateral ligament, and popping sounds are commonly caused by meniscal tears 2

MRI without IV contrast is the indicated next examination when initial radiographs are negative but pain and mechanical symptoms persist, with 96% sensitivity and 97% specificity for detecting meniscal tears 1, 3
MRI shortened diagnostic workup, reduced additional procedures, and improved quality of life in the first 6 weeks, potentially reducing productivity loss 1
Clinical examination alone has low diagnostic benefit in acute knee trauma, with higher-than-suspected incidence of injuries found on MRI 1

Do not dismiss the diagnosis simply because x-rays are negative, as x-rays only detect 83% of fractures and miss virtually all soft-tissue injuries 1
Popping with pain warrants investigation, as popping sounds with associated pain, swelling, or instability indicate potential structural damage requiring treatment 2
Avoid delaying MRI, as in patients <40 years old with acute knee injury, knee effusion >10 mm on lateral radiograph should prompt immediate consideration for knee MRI, which can decrease delayed diagnosis, improve outcomes, and decrease disability 1

The American College of Radiology recommends proceeding directly to MRI without IV contrast for evaluating suspected internal derangement when radiographs are negative, especially for persistent knee pain 5 days after injury with suspected ligamentous overstretch 4, 5, 6

MRI accurately evaluates ligamentous injuries with proven high accuracy: 74% sensitivity and 95% specificity for ACL tears, 81% sensitivity and 95% specificity for PCL tears, and excellent performance for collateral ligament assessment, according to the American College of Radiology 4, 5

CT without IV contrast may detect occult fractures but is inferior to MRI for soft-tissue evaluation, with only 79-87.5% sensitivity for ACL tears and low sensitivity for other soft-tissue injuries, as stated by the American College of Radiology 4, 6
Ultrasound is not the standard of care because its performance varies significantly with operator skill and patient factors, and it cannot comprehensively evaluate intra-articular structures like menisci and cruciate ligaments, according to the American College of Radiology 4

The American College of Radiology recommends ordering MRI knee without IV contrast immediately for a 5-day post-injury patient with negative X-ray and suspected ligamentous injury 4, 5, 7
MRI will definitively identify ligamentous tears, meniscal tears, bone marrow edema/contusions, occult fractures, joint effusion characteristics, and associated soft-tissue injuries, as stated by the American College of Radiology 4, 5