To our knowledge in medial unicompartmental knee arthroplasty (UKA) no study has specifically assessed the difference in outcome between matched gender groups. Previous unmatched gender studies have indicated more favourable results for women. Method. 2 groups of 40 of either sex was determined sufficient power for significant difference. These consecutively were matched with both the pre-operative clinical and radiological findings. Minimum follow up of 2 years, mean follow-up 5.9 years. Mean age at operation was 71 years. Results. In both groups, the mean IKS knee and function scores improved significantly (p< 0.001) post operatively. There were no significant differences were between the 2 groups. In both groups mean preoperative flexion was 130 degrees and remained unchanged at final follow-up. No significant differences in preoperative and postoperative axial alignment and in the number of radiolucent lines, between groups. With component size used there was a significant difference (p < 0.001) between the 2 groups. However the size of the femoral or tibial implant used was significantly related (p< 0.001) to patient height for both sexes. Radiolucent lines were more frequent on the tibial component, but were considered stable with none progressing. No revisions for component failure. 1 patient in each group developed lateral compartment degenerative change. Male group; one conversion to TKA for undiagnosed pain, three patients underwent reoperation without changing the implant. Female group; no implants were revised, and two patients required a reoperation. Kaplan-Meier 5-year survival rate of 93.46% (84.8; 100) for men and100% for women. The survival rate difference is not significant (p=0.28). Conclusion. These results suggest that there is no difference in outcome between
