A giant extrasynovial osteochondroma in the infrapatellar fat pad: end stage Hoffa’s disease

Abstract

The infrapatellar fat pad of Hoffa is commonly injured but rarely discussed in the orthopaedic literature. Hoffa's disease is the extension of various traumatic events due to impingement and inflammation of the infrapatellar fat pad and known as a vague reason for anterior knee pain. Inflammation is foreground during acute phase of the disease while impingement due to fibrosis and scar tissue of infrapatellar fat pad plays a major role in the chronic phase. The osteochondroma of the infrapatellar fat pad secondary to the Hoffa's disease can be more problematic. Although, the fibrocartilaginous transformation and osteochondral metaplasia of infrapatellar fat pad was pointed out frequently in the literature, the published papers seem far from clarifying the relation between chronic impingement and formation of osteochondroma. We present a case of a giant ossifying chondroma in the infrapatellar fat pad that resulted from chronic Hoffa's disease. Complete open resection was performed successfully after arthroscopic examination. The infrapatellar fat pad contains the entire progenitor cells for the development of an osteochondroma and chronic impingement may have promoter affect on this issue, thus, an osteochondroma may occur at the end-stage Hoffa's disease.

Function of the Infrapatellar Fat Pad and Advanced Hoffa's Disease With Ossification

“…This leads to differentiation into osteochondroma, which is however rare. 9 A study by Ushiyama et al 11 showed that this IFP has endocrine functions. It was found that cytokines involved in chondrocyte metabolism are produced in IFP, such as the basic fibroblast growth factor, vascular endothelial growth factor, tumor necrosis factor-alpha and interleukin-6.…”

“…These include Hoffa's disease, IFP ossification, solitary intraarticular chondroma, acquired intra-articular osteochondroma, intracapsular chondroma, para-articular chondroma/osteochondroma and capsular osteoma. 9 In Hoffa's syndrome, there is increased T 2 sequence signal due to edema and hemorrhage in MRI during the acute phase; and fibrin and hemosiderin build-up during the chronic phase. This is visualized as reduced T 1 and T 2 signals and a hypointense image on MRI.…”

“…The IFP contains these root cells which can transform into adipocyte cells containing chylomicron and releasing leptin, chondrocyte cells synthesizing the cartilage matrix and osteoblast cells that mineralize, depending on environmental conditions. 4 Turhan et al 9 presented a young patient diagnosed with Hoffa's syndrome. In this case, there was a history of trauma dating back to seven years ago, and an X-ray scan revealed ossific focus in the infrapatellar region.…”

Alterations in Hoffa’s fat pad induced by an inflammatory response following idealized anterior cruciate ligament surgery

“…ACL-R). Fibrosis of IPFP tissue could play a major role in the chronic phase of inflammatory diseases [26]. Fibrosis results from the accrual of extracellular matrix components due to excessive synthesis of collagens I, III, and VI, and impaired degradation of these proteins.…”

Osteochondromatosis and Osteochondroma Involving Bilateral Patella and Patellar Tendon: A Case Report

“…1,3,4 Patients may have abnormal scar formation. Fracture may occur in approximately 5% of bones with osteochondroma.…”