Moderate joint knee joint effusion with synovial thickening and frond-like synovial projections of fat-density and signal intensity; impressive of lipoma arborescens with degenerative joint disease and severe osteoarthritic changes of the knee joint as well as lateral femoral condyle subchondral cystic lesion; likely subchondral Geode rather than intraosseous ganglion or chondroblastoma with extensive perilesional osseous edema, degenerative tear of the posterior horn medial meniscus (PHMM), early mucoid degeneration of the ACL & a small pes anserinus bursitis.

Lipoma arborescens is idiopathic, however unusual nonspecific reactive response to chronic synovial irritation, either mechanical or inflammatory insults is suggested. It is considered as a lipoma-like benign synovial villous proliferation with replacement of the subsynovial connective tissue by mature fat cells.

The radiological signs are frond-like fat-density or signal intensity synovial lesions (ranging from small frond-like proliferations to large infiltrating fronds of hyperplastic synovium and eventually large rounded or globular fatty mass lesions) usually located within the suprapatellar bursa.

The clinical presentation is usually painless swelling of the knee, with pain later on from accelerated osteoarthritis and internal derangement of the knee. 

Treatment is synovectomy (before osteoarthritis and internal derangement prevail).