Introduction: Nowdays most of the health services focus on the reduction of expenses and the shorter hospital stay. For the patients is also important the faster rehabilitation in work and in full self-sufficiency.

Patients and methods: Möller has published in 1997, that medial unicompartmental knee arthroplasty can be operated from a shorter mediopatellar approach. This technique is important not only for the shorter wound, but much more for the faster rehabilitation because of the preserve of the extensor mechanism of the knee.

Between April 2000 and December 2002 we performed the minimal invasive medial unicompartmental knee arthroplasty in 36 cases. Our results were evaluated by the HSS knee score. The average follow up time was 24.7 months. We have compared our results to a similar group in age, number and follow up time, who has been operated in the traditional approach.

Results: However the overall HSS results showed significant difference (95.3 & 84.8), we think that the subgroups presents the substance of it much better. There was significant difference in walking distance, stair climbing, range of movement and muscle power, and we did not find any significant difference in pain, transport, flexion contracture, instability, need for appliance and the varus-valgus deformity.

Conclusion: In those cases, where both the patients win with the shorther rehabilitation and also the health service saves money with the reduction of expenses the minimal invasive way of operation should be more often used.