ABSTRACT
Osteonecrosis of the femoral condyle is known as an uncommon complication after arthroscopic meniscectomy. The lesion of osteonecrosis can be irreversible, thus early detection of the disease is crucial for treatment. A 50-year-old male patient without known risk factors of osteonecrosis developed increasing knee pain after arthroscopic partial meniscectomy. Magnetic resonance imaging showed rapid progression of osteonecrosis of the medial femoral condyle. Unicompartmental knee arthroplasty was performed after 9 months of conservative therapy. The patient is now free from pain during daily activities. It might be important to remind that if the patient's pain after arthroscopic partial meniscectomy is severe than expected, clinical doctors should pay attention to the possibility of ongoing osteonecrosis of the femoral condyle.