A 47-year-old man with progressive pain in the right knee for three years. He denies previous surgeries. On physical examination, the right knee displays pain without specificity in relation to a particular injured structure. The radiography showed a nonspecific lytic lesion in the proximal tibia (Fig. 1). CT demonstrates a medullary lesion in the proximal metaphysis of the ti bia, with a density of approximately 25 Hounsfield units, well demarcated without marginal sclerosis, with a non-aggressive aspect, compatible with intraosseous lipoma (Fig. 2). MRI displays a lesion in the proximal tibia with an isointense signal in relation to the subcutaneous fat on T1- and PD-weighted images (Fig. 3), confirming the CT diagnosis.

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Intraosseous lipomas are a benign tumor which have an incidence of less than one per 1000 cases of bone tu mors with a male predilection and a possible cause of non-traumatic bone pain. However, in more than 50% of cases, they are asymptomatic. Intraosseous lipomas are most commonly found in the metaphyseal and epiphyseal of bones, affecting the lower limbs in 71% of cases. Treatment is symptomatic, consisting of curettage and bone grafting. In asymptomatic patients, the conservative approach is the most indicated, with an excellent prognosis.