Large intra-articular true lipoma of the knee

Abstract

BackgroundIntra-articular lipomas are rare and very few cases have been reported in the knee. To the best of our knowledge, here we report the largest lipoma to have ever been observed in the knee. It is crucial to avoid the misdiagnose of lipoma arborescens, which is associated with degenerative joint disease. Lipoma is a homogeneous, ovoid, adipose tissue tumor that is contained within a fibrous capsule and not associated with previous disease.Case presentationA 48-year-old male, with a soft-tissue tumor on the superomedial aspect of the right knee. Magnetic resonance imaging (MRI) revealed an intra-articular lipoma. The mass was resected by means of a limited arthrotomy.ConclusionsKnee lipoma is an extremely rare disease that must be diagnosed by MRI. Where possible, it should be resolved by arthroscopic resection.

Tumor lipomatoso intra-articular do joelho: Dois casos similares, mas diferentes

“…Although initially described as different spectra of the same lesion (benign, chronic and slow-growing), 5 6 7 true intra-articular lipomas and the less rare LA are different in presentation and pathogenesis. 3 6 Lipomas arborescens are well established lipomatous lesions, characterized by the replacement of the subsynovial layer by mature fat cells in a villiform proliferated synovium, whose etiology is unknown.…”

“…Although initially described as different spectra of the same lesion (benign, chronic and slow-growing), 5 6 7 true intra-articular lipomas and the less rare LA are different in presentation and pathogenesis. 3 6 Lipomas arborescens are well established lipomatous lesions, characterized by the replacement of the subsynovial layer by mature fat cells in a villiform proliferated synovium, whose etiology is unknown. 1 2 3 5 7 The majority of LA is thought to rise from a nonspecific chronic synovial irritation and is usually associated with trauma, degenerative joint disease and inflammatory conditions (even the sparsely described psoriatic arthritis, like in case 1), yet a true causal relationship is difficult to establish.…”

“… 1 2 3 5 7 The majority of LA is thought to rise from a nonspecific chronic synovial irritation and is usually associated with trauma, degenerative joint disease and inflammatory conditions (even the sparsely described psoriatic arthritis, like in case 1), yet a true causal relationship is difficult to establish. 1 5 6 7 Lipomas arborescens seem to occur equally in both genders; 5 7 nonetheless, there are two types of LA: typical (secondary) are more common, larger, occur in older patients (bilateral occurrence in the knee is estimated in 20% of cases 1 2 7 ) and are often associated with other intra-articular pathology; on the other hand, atypical (primary) LAs are rarer, smaller, occur in younger patients, usually with monoarticular involvement or in other locations besides the knee, and present without other joint alterations 1 3 5 7 8 …”

“…As for intra-articular lipomas, they are rare de novo entities, usually solitary small fatty ovoid masses (unlike our case 2, which had an extremely rare morphology) that are involved by a fibrous capsule of synovial tissue; they can emerge from the synovial membrane or overgrow from the intra-articular subsynovial fat and are most commonly found in the knee over the femur in connection with the fat pads (suprapatellar, prefemoral – like in our case – or infrapatellar), although they can occur more rarely in other locations (e.g., hip, spine, elbow, shoulders and wrists). 3 4 6 …”

“…Most of them are benign and the knee is the most affected joint. 1 2 3 4 5 6 Regarding these, although few cases of lipoma arborescens (LA) have been described in the literature, true intra-articular lipomas are exceedingly rare. 3 4 6 Reporting two distinct cases of rare intra-articular lipomatous tumors, the authors intend to discuss their etiology, clinical and imaging aspects and treatment approach.…”