The results of 40 medial unicompartmental knee arthroplasties, performed by a single surgeon in a community hospital setting, with an average follow-up of 6 years (range, 3-10 years), were analyzed retrospectively. The Knee Society rating system was used, revealing an average score of 80.5 points and 79% good-to-excellent results. One patient required revision to total knee arthroplasty secondary to late infection. Five other patients (5 knees) required further surgery consisting of limited synovectomy and exchange of polyethylene insert at an average of 5.5 years. The 10-year survival rate using revision to total knee arthroplasty or aseptic loosening as an endpoint is 97%. The survival using any revision surgery as an endpoint was 74% at 10 years. Statistical analysis revealed that the most important factor for good-to-excellent results was patient age >65 years. Likewise, postoperative alignment was crucial in decreasing the rate of revision surgery. No other selection criteria were statistically significant in this series. We report favorable intermediate-term results in 40 unicompartmental knee arthroplasties; special attention to patient selection and postoperative alignment is essential to attain good-to-excellent results.