Background Patients who leave the hospital against medical advice are at risk for readmission and for a variety of complications and are likely to consume more healthcare resources. However, little is known about which factors, if any, may be associated with self-discharge (discharge against medical advice) among orthopaedic inpatients. Questions/purposes We studied the frequency and factors associated with self-discharge in patients hospitalized for orthopaedic trauma and musculoskeletal infection. Methods Using discharge records from the Nationwide Inpatient Sample (2002-2011), we identified approximately 7,067,432 patient hospitalizations for orthopaedic trauma and 5,488,686 for musculoskeletal infection. We calculated the proportions of admissions that ended in selfdischarge for both trauma and infection patients; then, we examined patient demographics, diagnoses, and hospital factors. Multivariable logistic regression models were constructed to determine independent predictors of selfdischarge. Results Approximately one in 333 (0.3%) patients hospitalized for an isolated fracture and one in 47 (2.1%) patients with musculoskeletal infection left against medical advice. Patient characteristics associated with self-discharge included age \ 75 years (trauma: odds ratio [OR] 2.7, 95% confidence interval [CI] 2.5-2.8, p \ 0.001; infection: OR 3.9, 95% CI 3.8-4.1, p \ 0.001), male sex (trauma: OR 1.7, 95% CI 1.7-1.8, p\0.001; infection: OR 1.4, 95% CI 1.3-1.4, p \ 0.001), black race/ethnicity (trauma: OR 1.5, 95% CI 1.4-1.6, p\0.001; infection: OR 1.1, 95% CI 1.1-1.1, p \ 0.001), low household income (trauma: OR 1.5, 95% CI 1.4-1.5, p\0.001; infection: OR 1.4, 95% CI 1.4-1.4, p \ 0.001), nonprivate insurance (Medicare [trauma: OR 1.7, 95% CI 1.6-1.8, p \ 0.001; infection: OR 2.5, 95% CI 2.4-2.5, p \ 0.001] and Medicaid [trauma: OR 2.6, 95% CI 2.5-2.7, p \ 0.001; infection: OR 3.2, 95% CI 3.2-3.3, p \ 0.001]), and no insurance coverage (trauma: OR 3.0, 95% CI 2.9-3.1, p \ 0.001; infection: OR 3.5, 95% CI 3.4-3.5, p \ 0.001), less medical comorbidity (trauma: OR 0.94 per one-unit increase in the number of comorbidities, 95% CI 0.93-0.95, p\0.001; infection: OR 0.88, 95% CI 0.87-0.88, p\ 0.001), alcohol (trauma: OR, 2.3, 95% 2.2-2.4, p \ 0.001; infection: OR 1.5, 95% CI 1.5-1.5, p \ 0.001), opioid (trauma: OR 2.9, 95% CI 2.7-3.1, p\0.001; infection: OR 4.4, 95% CI 4.3-4.4, p \ 0.001) and nonopioid drug abuse (trauma: OR, 2.0, 95% CI 1.9-2.1, p \ 0.001; infection: OR 2.8, 95% CI 2.8-2.9, p \ 0.001), psychosis (trauma:Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. 3, 95%CI 1.2-1.3, p\0.001; infection: OR 1.3, 95% CI 1.3, 1.4, p \ 0.001), and AIDS/HIV infection (trauma: OR 1.5, 95% CI 1.2-1.8, p\0.001; infection: OR 1.3, 95% CI 1.3-1.4, p \ 0.001). Patients with upper...