Figure 1. Posteroanterior (a) and lateral (b) radiographs of the left knee: A well-defined radiolucent lesion in proximal metaphysis of tibia is noted. The lesion does not show the usual well-defined marginal sclerosis. Note also thickening of the cortices of tibia

From

The "Penumbra Sign" on Magnetic Resonance Images of Brodie's Abscess: A Case Report and Literature Review

Farate A, Yunusa GH, Umar UH, Ahmadu MS, Mustapha Z, Ahidjo A

American Journal of Medical Case Reports. 2017, 5(8), 199-201 doi:10.12691/ajmcr-5-8-1