The original Oxford and Low Contact Stress mobile-bearing unicompartmental knee designs have been used successfully since the mid-1970s, but have had limited exposure. Our study reviews 177 LCS unicompartment replacements (156 medial) with 5-19 years follow-up. Mean age was 68 years, 70% were female, with osteoarthritis (OA) diagnosis in 96%. Fixation was cementless in 72% and cemented in 28%. Results were good/excellent [modified Hospital for Special Surgery (HSS)] in 82%. Scores improved from 60 to 86, mean range of motion 123 degrees. Complications requiring reoperation were 32 of 177 knees (18%). Early failures were technique-related and late failures (3+ years) related to bearing wear/fracture; 15 cases required bearing exchange alone. Low contact stress mobile-bearing unicompartmental knee arthroplasties with 82% prosthetic survivorship at 11 years is encouraging, especially in a more active population and with the success of bearing exchange.