| Image Quiz |
| Spontaneous Versus Atraumatic Osteonecrosis of the Knee1 (continued) |
| Answer: Atraumatic osteonecrosis of the femur and the tibia. |
Fig. 2 |
Fig. 2 Coronal fat-suppressed T2-weighted image showing atraumatic osteonecrosis of the femur and the tibia.
For larger view, click on image |
| Discussion |
| Table I differentiates two entities: spontaneous and atraumatic osteonecrosis of the knee. |
| TABLE I Osteonecrosis |
|
Parameter
|
Spontaneous Osteonecrosis of the Knee
|
Atraumatic Osteonecrosis of the Knee
|
|
Synonyms
|
SPONK, SONK
|
Secondary or steroid-associated osteonecrosis
|
|
Location
|
Medial femoral condyle
|
Multiple condyles, tibial involvement in 20%
to 30%
|
|
Distribution
|
Subcortical
|
Epiphyseal, metaphyseal, and diaphyseal common
|
|
Age of patients
|
Usually >60
yr
|
Usually <45
yr
|
|
Bilateral knee involvement
|
<1%
|
>80%
|
|
Hip involvement
|
None
|
90%
|
|
Associated risk factors
|
Rare
|
>80%
(e.g., steroids, alcohol)
|
|
Pathogenesis
|
May represent microtrauma, osteoarthritis,
or osteopenia
|
Multiple theories regarding etiology
|
|
| Reference |
1. Khanna AJ, Cosgarea AJ, Mont MA, Andres BM, Domb BF, Evans PJ, Bluemke DA, Frassica FJ. Magnetic resonance imaging of the knee. Current techniques and spectrum of disease. J Bone Joint Surg Am. 2001;83 Suppl 2 Pt 2:128-41. |
