What is the role of MRI in septic arthritis (SA) imaging?

Updated: May 12, 2016
  • Author: Lourdes Nunez-Atahualpa, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Answer

Synovial enhancement and the presence of a joint effusion have been reported to have the highest correlation with the clinical diagnosis of a septic joint. Bone erosions, bone marrow edema, cartilage loss, and erosion enhancement have also been identified, particularly in the setting of bacterial infections. [5]

Patients with nonpyogenic arthritides, such as lyme disease, may present with massive recurrent joint effusions. In the knee joint, an association with uniform cartilage loss, enthesitis, popliteal fossa lymphadenopathy, and popliteal muscle myositis has been described. [5]  Patients with tuberculous arthritis may have more bone erosions and less marrow-signal abnormality on MRI than patients with pyogenic arthritis. Use of intravenous gadolinium contrast is also very helpful in patients with a suspected septic joint to distinguish a periarticular abscess from surrounding myositis and to evaluate the degree of synovial inflammation. [2]

It has been suggested that MRI should be used in the first 12 hours to diagnose concurrent infections in newborns and in adolescents, as well as involvement of the shoulder joint, symptomatic arthritis of more than 6 days, and infection by methicillin-susceptible Staphylococcus aureus (MSSA) or methicillin-resistant S aureus (MRSA). [33]

When dynamic contrast-enhanced MRI is used, the signal intensity at 3.5 minutes (2.7-4.3 min) could be considered as a fair way to help differentiate SA from transient synovitis in the hip joint. [34]

Decreased intensity is expected when compared to contralateral joint. [34]

In vivo MR studies marking macrophages with nanoparticles, such as ultrasmall supermagnetic iron oxide, and with later follow-up are being performed to detect early synovial inflammation and monitor treatment  [35, 36]


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