Arborescent lipoma is an unusual intra-articular lesion that typically develops in the knee and has to be evoked before chronic effusion. It corresponds to hyperplasia of mature fatty tissue and hypertrophy of synovial villi, developing within a joint. The reference treatment is synovectomy by arthrotomy. The rare forms localized to the anterior compartment of the knee can benefit from an arthroscopic synovectomy. The authors report a case of arborescent knee lipoma in a 47-year-old patient who received arthroscopic synoviectomy. To our knowledge, only a few cases of arborescent lipoma treated by arthroscopic synoviectomy have been reported in the literature.