Resinous lipoma belongs to a special type of lipoma, also called synovial choriocapillaris lipomatous hyperplasia, which mostly occurs in the synovium of the knee joint and suprapatellar bursa.
Resinous lipoma is grayish white, grayish-yellow, mostly in knee joint and suprapatellar bursa, most of them are due to the long time damage of cartilage in the joint, synovial membrane forms dendritic lipoma, which is a kind of adaptive and protective hyperplasia.
Fiberoptic microscopic observation of synovium showed choroidal hyperplasia, infiltration of mature adipocytes in the subsynovial layer, and a large number of dilated and congested capillaries within the choroid.
The pathogenesis of resinous lipoma is not completely clear. It is considered to be the result of infiltration of synovial membrane by mature adipocytes with chorioallantoic hyperplasia. It is considered to be a non-specific response of synovial tissue to long-term chronic irritation.