Avascular necrosis of the knee in retroviral disease

Case contributed by Domenico Nicoletti
Diagnosis certain

Presentation

Left knee pain without trauma in an HIV positive subject receiving antiretroviral therapy.

Patient Data

Age: 40 years
Gender: Male

There are no bone lesions.

There are serpiginous areas of low signal intensity on the T1W images in the distal femoral condyles and lateral tibial plateau. A low-signal-intensity rim delineates the areas of infarct. There is extensive bone marrow edema with high-signal-intensity serpiginous rims on the PD fat sat sequences.

Case Discussion

The definition avascular necrosis should be used when bone involvement occurs in the epiphyseal region or subchondral bone. While talking about bone infarcts when the involved areas are the metaphysis or diaphysis, although such infarcts may extend up to the epiphysis or subchondral bone. Avascular necrosis is usually post-traumatic, occurring after a femoral neck fracture or hip fracture-dislocation. In the absence of prior trauma, osteonecrosis is usually bilateral and occurs in younger subjects. HIV-infected individuals have an increased risk of avascular bone necrosis (AVN). Antiretroviral therapy and particularly protease inhibitors have been implicated as a risk factor.

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