Introduction:The management of isolated unicompartmental osteoarthritis in the patient aged 70 years and older is an issue of debate. The purpose of the present study was to retrospectively evaluate the outcomes of patients aged over 70 years who underwent unicompartmental knee replacement (UKR) for the treatment of isolated unicompartmental osteoarthritis. The hypothesis was that this represents a safe and viable procedure leading to improved functional outcome in elderly patients affected by isolated unicompartmental osteoarthritis. Methods: 22 consecutive medial compartment UKRs performed between 1998 and 2008 were retrospectively evaluated. Mean age was 74 years (range 70-93 years). Patients were evaluated preoperatively and after an average follow-up of 6.2 years (range 2 to 8). Assessment included KOOS score, WOMAC score, Knee Society Score. Standard X-rays were performed prior to surgery and at follow-up. Results: Twenty patients showed a statistically significant improvement in all parameters. One patient who was 93 years old at the time of surgery died for unrelated causes. One patient required conversion to a total knee arthroplasty. Discussion: UKR is a safe and clinically effective procedure, which has been proven valuable for the treatment of elderly patients with isolated unicompartmental osteoarthritis and with initial degenerative signs in the other compartments. Conclusion: Age more than 70 does not appear to be a contraindication to the procedure. Level of evidence: IV (case series).KEY WORDS: unicompartmental osteoarthritis, medial knee osteoarthritis, unycondilar knee replacement, elderly people.