MRI Determination of Knee Osteoarthritis

Indications for MRI in Osteoarthritis Assessment

The American College of Radiology recommends MRI without IV contrast when radiographs are normal or show only joint effusion but pain persists, as it is the next indicated examination 4
MRI is appropriate for identifying pain generators in established osteoarthritis, detecting bone marrow lesions (BMLs) and synovitis/effusion, which are potential sources of knee pain in osteoarthritis patients 5, 4
The American College of Radiology suggests that MRI without IV contrast is not usually indicated in patients for whom radiographs are already diagnostic of osteoarthritis, unless symptoms are not explained by the radiographic findings 1, 2, 3

MRI detects bone marrow lesions (BMLs) with edema-like signal in subchondral bone, and new or increasing BMLs correlate with increased knee pain, especially in males or patients with a family history of osteoarthritis 5, 4
MRI identifies synovitis and effusion, which may indicate the origin of knee pain in osteoarthritis 5, 4
Meniscal tears are detected in all osteoarthritic knees, though often incidental in older patients 4
Subchondral cysts and bone attrition are also detected by MRI 4

The American College of Radiology notes that the ability to discriminate painful from nonpainful knees is limited, especially in patients over 70 years of age, since bilateral structural abnormalities can be present with primarily unilateral symptoms 1, 2, 3
Meniscal tears are often incidental, and the likelihood of a tear is not significantly different between painful and asymptomatic knees in patients 45-55 years 4
MRI findings do not always correlate with symptoms, even using synovitis/effusion presence or Kellgren-Lawrence score of 2, discrimination between painful and asymptomatic knees remains limited 1, 2, 3

The American College of Radiology recommends starting with weight-bearing radiographs (posteroanterior, lateral, sunrise patellar views) 5, 6
If radiographs are diagnostic of osteoarthritis and symptoms match the radiographic findings, MRI is not indicated 1, 2, 3
If radiographs are normal or show only effusion but pain persists, proceed to MRI without IV contrast 4
If radiographs show osteoarthritis but symptoms are unexplained, MRI without IV contrast is indicated 1, 2, 4