Indications for UKA for isolated osteoarthritis of the knee remain controversial. Two hundred twenty-nine UKA that were performed at our institution were evaluated for which factors were associated with a poor outcome. BMI >35 was correlated with lower KSS scores than patients with BMI <35. In contrast to prior reports, patients younger than 60 years old had higher scores than patients 60 years and older at 2 years. Women had an unacceptably high short-term revision rate for any reason of 6.5%. Popularity for UKA has increased, and a more in depth investigation of predictors of poor outcomes demonstrates that younger patients appear to have better results. Obese patients continue to improve up to 2 years after surgery and should not be precluded from undergoing UKA.