Avascular necrosis, SONK, femur and patella

Case contributed by Dr Nafisa Shakir Batta


Pain at the knee

Patient Data

Age: 50 years
Gender: Male

Left knee reveals an unstable old osteochondral fracture with secondary degenerative changes.

Medial condyle of distal femur shows a detached osteochondral fracture with sequestrum and large area of cartilage and cortical loss (stage 5 injury). Perilesional free fluid (rim sign) & articular cortex buckling are noted with  secondary osteophytes, corner erosion, and marrow edema  are seen at medial tibial condyle.

Irregular serpiginous sclerotic areas of nonviable bone marrow with surrounding edema are seen at medial condyle, trochlear fossa and posterior lateral condyle of femur, consistent with Avascular necrosis.

The medial meniscus is partially fragmented and  shows a  bucket handle radial tear with displaced fragment in intercondylar fossa (double PCL sign). This is likely sequel to mechanical stresses from the buckled femoral condyle.

The patellofemoral articulation shows degenerative changes with osteochondral fracture at articular margin of medial facet of patella with a continuous overlying cortical and cartilaginous outline.(stage 3 injury).

Interstitial edema is seen at medial patellofemoral ligament (MPFL).

Small volume joint effusion is also evident with a multilobulated cystic structure in close relationship to PCL, compatible with PCL ganglion cyst.




Case Discussion

MRI left knee reveals a osteochondral injury at medial femoral condyle and patella, foci of avascular necrosis at distal femur, full thickness medial meniscal tear with bucket handle tear, PCL ganglion cyst and marked arthrosis at medial tibiofemoral and patellofemoral articulation.

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