Risk factors for failure of manipulation under anesthesia in posttraumatic knee stiffness

•Over half of the patients who received manipulation under anesthesia (MUA) for posttraumatic knee stiffness required subsequent treatment.•We identified three factors associated with MUA failure, including delayed first MUA, neurologic injury, and worse pre-procedure knee flexion.•The likelihood of obtaining adequate range of motion (ROM) with MUA alone observed in the sample is lower than in previous studies.•Patients in the study had a higher likelihood of an additional MUA or surgical release to obtain adequate ROM than in previous research. To determine the proportion of patients who fail manipulation under anesthesia (MUA) as a treatment for posttraumatic knee stiffness and determine the risk factors for MUA failure. A retrospective cohort study was performed at a level I trauma center. We identified 213 knees in 199 patients with arthrofibrosis treated by MUA within 1 year of injury from 2007 to 2020. The primary outcome was MUA failure as defined by need for repeat MUA or surgical release after MUA. Multivariable logistic regression was used to determine the association between MUA failure and potential risk factors. Overall, 111 knees (52%) failed treatment with MUA. An association was demonstrated between MUA failure and delay in treatment >90 days after injury (OR 3.6, p