Age / Sex : 41 / M

Chief complaint: Intermittent left knee pain during 3 years

What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

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Courtesy: 이영환 (Young Hwan Lee), 대구가톨릭대학교병원 (Daegu Catholic university Medical Center)

Gouty arthritis

Discussion

Findings:

MR images show heterogeneous signal intensity in and around the posterior cruciate ligament, proximal portion of popliteal tendon, patellar articular cartilage. The lesions have intermediate signal intensity on T1-weighted image and intermediate to low signal intensity on T2-weighted image. Nearby the lesions, femoral insertion sites of posterior cruciate ligament and popliteal tendon show bony erosion. And associated mild marrow edema is seen.

Differential Diagnosis:

Gouty arthritis

Pigmented villonodular synovitis

Diagnosis:  

Gouty arthritis

Discussion:

The musculoskeletal manifestation of gout are triggered by the deposition of monosodium urate(MSU) crystals in cartilage, joints, and periarticular soft tissue. Medial aspect of the first metatarsophalangeal joint, is a common site of involvement. Another common site of involvement is the knee and ankle. Gout deposits around joints can be juxta-articular, intra-articular, as well as located in tendons and subcutaneous tissue and usually do not demonstrate symmetric joint involvement. The tophus, the hallmark of chronic gout, is a soft tissue nodule representing the body’s granulomatous immune reaction to MSU crystals. Dense calcification in the tophus may be found. Erosions are often located next to a tophus.

The MRI feature of tophi have intermediate or low signal intensity on T1 weighted images and heterogeneous signal intensity on T2 weighted images, possibly because of the presence of variable amount of calcium. Tophi can show uniform enhancement or show a nonenhancing center. Because, a tophus consists of central acellular crystalline core and a peripheral fibrovascular zone. Bone erosions adjacent to tophi can produce cortical destruction and variable bone marrow edema.

There are specific tendons about the knee that are commonly involved with gout, such as the popliteus and patellar tendons. Intratendinous tophus may present as a mass and clinically may appear as a soft tissue malignancy.

References

Gandikota Girish, Katrina N. Glazebrook, Jon A. Jacobson. Advanced imaging in gout. AJR 2013;201:515-525

Gandikota Girish, David M. Melville, Gurjit S. Kaeley, et al. Imaging appearances in gout. Arthritis 2013;2013:673401