Introduction Manipulation under anesthesia (MUA) is a standard treatment for arthrofibrosis after total knee arthroplasty (TKA), with reported rates of 1.5-6%. Customized TKA may have better outcomes by matching individual patient anatomy. However, a previous study reported an unacceptably high rate of MUA for customized TKAs. This study reports the incidence of MUA in a large cohort of second generation customized TKAs. Methods:Data was collected prospectively on 360 2nd generation ConforMIS

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... otal cruciate retaining TKAs. MUA was performed for clinically significant arthrofibrosis. Range of motion (ROM) and New Knee Society Scores (KSS) were evaluated at regular intervals for two years. Results: 11/360 (3.05%) knees underwent MUA. ROM overall improved from 115° to 125°, and from 112° to 122° in patients undergoing MUA. KSS objective and functional scores in MUA patients increased from 57 to 98 and 41 to 90, respectively, and in the entire cohort increased from 65 to 96 and 45 to 86 at 2 years (p<0.05). No MUA patients underwent revision surgery. Discussion and Conclusion:Customized TKA with second generation ConforMIS iTotal implants results in a MUA rate consistent with the literature for all designs. Additionally, patients exhibit significant increases in ROM and Knee Society Scores.