The osteonecrosis of the medial femoral condyle, depending on the area occupied, causes pain and may progress into osteoarthritis. For the management of osteonecrosis numerous treatment methods have been described, as conservative, drilling, osteotomy and others. The aim of our study is to evaluate the results of management of knee osteonecrosis with unicompartmental arthroplasty. We studied 16 knees in 15 patients (all women) with osteonecrosis of the medial femoral condyle. The size of osteonecrosis was greater than 3.5 cm, as revealed by MRI. The mean age of patients was 72 years (range 64–80 years). The time elapsed from the onset of symptoms to surgical treatment ranged from 3 to 10 months. All patients were followed clinically and by X-ray 1 to 6 years post-operatively and scored with Knee Society Score. The result in 14 patients was excellent and in 1 was good. In conclusion, unicompartmental knee arthroplasty is a satisfactory method of treatment of osteonecrosis, which provides immediate relief from pain, long-term satisfactory outcome and avoids multiple operations