Lower extremity osteoarthritis with concomitant low-back pain (LBP) may obscure a clinician’s ability to properly evaluate the status of hip or knee osteoarthritis and subsequent total joint arthroplasty (TJA) candidacy. A prospective cohort study was conducted to determine prevalence and severity of preoperative LBP among TJA patients, and the effect of TJA on alleviating LBP. Preoperative moderate to worst imaginable LBP pain on the Oswestry Disability Index (ODI) was significantly higher among hips compared to knees (28.8% vs. 16.1%, P < 0.0001). Compared to knees, hips also saw significant ODI improvement from preoperative to one-year postoperative. TJA candidates with considerable preoperative LBP should be counselled that TJA outcome may be impaired by the coexistence of spine disease, and that residual spine pain may continue following otherwise successful TJA.