Para-articular Osteochondroma of the Infrapatellar Fat Pad

ABSTRACT

We report a rare case of para-articular osteochondroma of the infrapatellar fat pad. A 56-year-old woman presented with a 2-year history of mild anterior knee pain and a hard mass around the right knee. Plain radiographs and computed tomography revealed trabeculated ossification within the infrapatellar fat pad. We performed surgery through an open approach. The mass was located within the infrapatellar fat pad and did not communicate with the joint space or patellar tendon. The gross appearance of the tumor resembled an osteochondroma. On microscopic examination, it was composed of cartilaginous tissue with areas of multifocal endochondral ossification surrounded by fibrous connective tissue. There was no synovial tissue. We diagnosed it as a para-articular osteochondroma of the infrapatellar fat pad. In the literature, this entity is rare. Differential diagnosis includes a variety of bone-forming lesions including malignancy. Definitive diagnosis is made by combining clinical, radiologic, and histologic findings.

KEYWORDS

Para-articular osteochondroma - ossification - infrapatellar fat pad - metaplasia

REFERENCES

• 1 Böstman O, Karaharju E, Heikkonen L, Holmström T. Extraskeletal ossifying chondroma in the knee. A case report.  Acta Orthop Scand. 1985;  56 87-89
• 2 González-Lois C, García-de-la-Torre P, SantosBriz-Terrón A, Vilá J, Manrique-Chico J, Martínez-Tello J. Intracapsular and para-articular chondroma adjacent to large joints: Report of three cases and review of the literature.  Skeletal Radiol. 2001;  30 672-676
• 3 Krebs V E, Parker R D. Arthroscopic resection of an extrasynovial ossifying chondroma of the infrapatellar fat pad: End-stage Hoffa's disease?.  Arthroscopy. 1994;  10 301-304
• 4 Milgram J W, Dunn E J. Para-articular chondromas and osteochondromas: A report of three cases.  Clin Orthop Relat Res. 1980;  (148) 147-151
• 5 Mosher Jr J F, Kettelkamp D B, Campbell C J. Intracapsular or para-articular chondroma. A report of three cases.  J Bone Joint Surg Am. 1966;  48 1561-1569
• 6 Rodriguez-Peralto J L, Lopez-Barea F, Gonzalez-Lopez J. Intracapsular chondroma of the knee: An unusual neoplasm.  Int J Surg Pathol. 1997;  5 49-54
• 7 Sakai H, Tamai K, Iwamoto A, Saotome K. Para-articular chondroma and osteochondroma of the infrapatellar fat pad: A report of three cases.  Int Orthop. 1999;  23 114-117
• 8 Steiner G C, Meushar N, Norman A, Present D. Intracapsular and paraarticular chondromas.  Clin Orthop Relat Res. 1994;  (303) 231-236
• 9 Carmont M R, Davies S, van Pittius D G, Rees R. Accelerated para-articular osteochondroma formation within the knee: A case report.  Cases J. 2008;  1 6
• 10 Hagan P F, Schoenecker P L. Para-articular osteochondroma.  Am J Orthop. 1995;  24 65-67
• 11 Li C, Arger P H, Dalinka M K. Soft tissue osteochondroma. A report of three cases.  Skeletal Radiol. 1989;  18 435-437
• 12 Milgram J W, Jasty M. Case report 238: Para-articular osteochondroma of the knee.  Skeletal Radiol. 1983;  10 121-125
• 13 Neves N, Gutierres M, Paiva M E, Cabral A T. Para-articular osteochondroma: A case report.  Rev Chir Orthop Repar Appar Mot. 2004;  90 71-74
• 14 Reith J D, Bauer T W, Joyce M J. Paraarticular osteochondroma of the knee: Report of 2 cases and review of the literature.  Clin Orthop Relat Res. 1997;  (334) 225-232
• 15 Rizzello G, Franceschi F, Meloni M C et al.. Para-articular osteochondroma of the knee.  Arthroscopy. 2007;  23 910 e1-e4
• 16 Turhan E, Doral M N, Atay A O, Demirel M. A giant extrasynovial osteochondroma in the infrapatellar fat pad: end stage Hoffa's disease.  Arch Orthop Trauma Surg. 2008;  128 515-519
• 17 Robillard G L. Ossification of infrapatellar bursae and fat pad.  Am J Surg. 1941;  51 442-444
• 18 Kautz F G. Capsular osteoma of the knee joint. Report of four cases.  Radiology. 1945;  45 162-167
• 19 Jaffe H. Tumors and Tumorous Conditions of the Bones and Joints. Philadelphia, PA: Lea and Febiger; 1958: 567
• 20 Wickham M Q, Erickson G R, Gimble J M, Vail T P, Guilak F. Multipotent stromal cells derived from the infrapatellar fat pad of the knee.  Clin Orthop Relat Res. 2003;  (412) 196-212