Purpose: There has been little study of whether total knee replacement (TKR) recipients from vulnerable populations-- including racial and ethnic minorities, the poor, the elderly, and those who are less well-educated-- are more likely to have surgery in low volume hospitals, which have higher rates of perioperative complications. Methods: We used Medicare claims to identify a national cohort of US Medicare beneficiaries who had elective TKR in 2000. Claims also provided individual level sociodemographic information. Census tract data provided neighborhood level sociodemographic features. We derived a summative measure of neighborhood vulnerability that included four high-risk neighborhood characteristics (proportion of residents with low income, low education, minority and foreign born status). We defined a low volume hospital (LVH) as a center performing <26 TKRs in Medicare patients in 2000. We used geocoding to identify ‘bypassers' (patients who had a higher volume hospital closer to their residence than the one where they had TKR). In multivariate logistic regression analyses, we examined the association of patient and neighborhood characteristics with utilization of LVHs and ‘bypassing'. Results: Of 113,015 Medicare TKR recipients, 13,120 (12%) utilized LVHs. Of these, 9815 (74.8%) bypassed a higher volume hospital. Multivariate analyses revealed that nonwhites (OR=1.24, 95% CI: 1.16-1.33), those who were poor (OR=1.94; 95% CI: 1.83-2.08), and those living in a non-urban area (OR=1.94; 95% CI: 1.87-2.01) were more likely to utilize LVHs. TKR recipients from neighborhoods with three or four vulnerability factors were about twice as likely to use a LVH and bypass a high volume hospital than patients living in neighborhoods with no vulnerability factors. Conclusions: Poor, less educated, rural patients and patients from urban areas with high concentrations of ethnic minorities, foreign-born and/or poor residents were most likely to choose a low volume hospital or bypass a higher volume center. These findings suggest that efforts to disseminate information about the association of volume with outcomes should target patients in rural locations and vulnerable populations in urban settings. Such efforts may improve the quality of care for TKR patients.