Lipoma arborescens: comparison of typical and atypical disease presentations.

AIM: To determine whether the aetiology differed between typical cases of lipoma arborescens with unilateral knee involvement and atypical cases involving joints other than the knee, polyarticular disease, and disease outside of the knee joint.
MATERIALS AND METHODS: Cases of lipoma arborescens involving the knee joint were evaluated for the distribution of the disease and severity of degenerative arthritis. Joints other than the knee were evaluated for the presence and severity of degenerative arthritis, and the distribution was classified as either intra-articular, extra-articular, or both. Clinical history was reviewed for patient age at presentation, a history of inflammatory arthritis, diabetes mellitus, and known steroid use. Fisher's exact test was used to determine whether there was a statistically significant difference between typical and atypical presentations of the disease.
RESULTS: Lipoma arborescens was identified in 45 joints in 39 patients. Twenty-eight patients were classified as "typical" and 11 patients had "atypical" disease. There was no significant difference in age at presentation, presence of degenerative arthritis, or known inflammatory arthritis when comparing typical and atypical presentations of the disease.
CONCLUSION: Twenty-eight percent of patients in the present study had atypical presentation of lipoma arborescens with multifocal lipoma arborescens or disease in joints other than the knee. There was no significant difference in age at presentation, presence of degenerative arthritis, or known inflammatory arthritis when comparing typical and atypical presentations of the disease. Of the 39 patients, only three had no evidence of degenerative arthritis, which suggests that many cases of lipoma arborescens are secondary to chronic reactive change in association with degenerative arthritis.