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Challenge of the Unknowns—Unknown 3

Radiographic Findings and Differential Diagnosis

Click images to review films and listen to further audio discussion by Dr. Renee DeVries


Minimal medial compartment joint space narrowing is noted. Note the thin, linear radiopacities in the medial and lateral joint spaces. A linear radiopacity is also seen paralleling the surface of the femoral condyles. Minimal osteophytic formation is seen at the patellofemoral joint.


The differential diagnosis for this case should include different types of arthritis. Arthropathies are divided into three categories: degenerative, inflammatory, and crystalline. Degenerative joint disease and diffuse idiopathic skeletal hyperostosis (DISH) are types of degenerative arthritis. Inflammatory arthropathies include conditions such as rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, etc. Gout, Calcium pyrophosphate dihydrate deposition disease (CPPD), and calcium hydroxyapatite crystal deposition disease (HADD) are examples of crystalline arthropathy.

In this case the following conditions might be considered in the differential diagnosis:

Degenerative Joint Disease


Calcium pyrophosphate dehydrate deposition disease (CPPD)



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Introduction to Unknown Cases

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