Abstract
BACKGROUND: "False patellar duplication" is a situation where there are two pieces in the position of a knee-joint like patella. It can derive from cartilage tumors, soft tissue tumors, or gout tumors, or due to the heterotopic ossification, forming a sub patella in the knee joint. CASE REPORT: A woman, 57 years old, healthy history, she has hospitalized for right knee joint pain since 2 years. Diagnosis: the synovial osteochondromatosis of the right knee. We decided to conduct and arthroscopy and removal. After 18 months surgery, the patient knee joint is currently good, range of motion (ROM) (-10)°- 0°-160°, Lysholm Knee Scoring Scale 85/100 point. CONCLUSION: This is the second case in the world and the first case in Vietnam. This is an experience in the process of diagnosis, arthroscopic treatment and differentiation from the "double patellae" status.