This study identified factors associated with an improvement in low back pain (LBP) at six-month follow-up after total hip arthroplasty (THA). Data from a national registry of 3054 patients were analyzed. Factors under analysis included demographics, comorbid conditions, operative and nonoperative joint pain severity, physical function, and mental health. Differences in these factors between patients with and without improvement in LBP were examined. Among patients reporting severe or moderate LBP preoperatively, 56% improved 6months after surgery. Patients without improvement were more likely to be on Medicare, have a high school education or less, have household income less than $45,000 and have one or more comorbid conditions. Patients with improvement in LBP experienced more resolution of pain in both the operative and nonoperative hip.