Extraskeletal Para-Articular Osteochondroma of Hoffa’s Fat Pad

Abstract

Extraskeletal para-articular osteochondromas are rare benign intracapsular tumours. They occur due to osteocartilaginous metaplasia in the para-articular soft tissue in the elderly. We report the same in the knee in a young patient, arising from Hoffa’s fat pad. A 26-year-old male presented with a gradually enlarging anterior left knee swelling of 3-year duration and inability to flex the knee fully. Clinical and radiological evaluation detected an ossified mass in Hoffa’s fat pad with features of osteochondroma. He underwent an excision of the mass and histopathology confirmed the diagnosis of extraskeletal para-articular osteochondroma. He was asymptomatic with functional improvement at 5-month follow-up. Extraskeletal para-articular osteochondromas are slow-growing, benign extrasynovial tumours arising in soft tissues with rare occurrence. They can present even in young and can only be diagnosed with a high index of suspicion, radiological features and clinicopathological correlation. They have to be distinguished from synovial chondromatosis and chondrosarcoma. It can be treated by surgical excision without any recurrence. If left untreated may lead to patellar tendinopathy and functional limitations.

Keywords

• extraskeletal osteochondroma
• hoffa’s fat pad
• knee swelling
• osteocartilaginous metaplasia