Inferior dislocation of patella after a total knee replacement-a case report

Acute inferior dislocation of the patella is rare but has been documented. However, there has been no published report of inferior dislocation of the patella following a total knee replacement (TKR). A 62-year-old man underwent a posterior cruciate retaining TKR Anatomic Graduated Component (AGC) (Biomet, Warsaw, IN) without patellar resurfacing. Perioperative events were unremarkable. The patient presented a year later with an acutely painful locked knee at 60 degrees flexion. Physical examination and radiographs confirmed an inferior dislocation of the patella due to interlocking of superior pole patellar osteophytes on the anterior edge of the intercondylar box of the femoral component. Closed reduction under anesthesia failed and open reduction with debridement of the osteophytes resulted in excellent patellar tracking and a good functional result without any recurrence. Surgeons need to be aware of this rare complication of acute locked knee following TKR which may require open reduction. Also, the debridement of the osteophytes or even a resurfacing of the patella may be a more definitive solution to such patellofemoral problems.