Retrospective review of 1216 primary total knee arthroplasties (TKAs) to evaluate incidence and predictors of arthrofibrosis, defined as flexion less than 90 degrees 1 year post-TKA. Incidence of stiffness post-TKA was 3.7% (45/1216). A matched case-control study was then conducted to identify predictive factors for this outcome. Preoperative flexion and intraoperative flexion were predictive of ultimate postoperative flexion (P = .001 and P = .039, respectively). There was no correlation between postoperative stiffness and specific medical comorbidities, including diabetes. Preoperative and postoperative relative decreased patellar height and stiffness postoperative were significantly correlated (P = .001). Although stiffness post-TKA is multifactorial, careful attention to surgical exposure, restoring gap kinematics, minimizing surgical trauma to the patellar ligament/extensor mechanism, appropriate implant selection, and physiotherapy combined with a well-motivated patient may all serve to reduce the incidence of stiffness post-TKA.