63 patients with uni- or bilateral osteoarthritis were randomized to 2 groups that underwent mobile-bearing (MB) total knee arthroplasty (TKA) or fixed-bearing (FB) TKA. Over a 2 year follow-up period, total translation (TT) via radiostereometric analysis (RSA), bone mineral density (BMD), correlation between implant migration and BMD, and Oxford knee scores (OKS) were evaluated. Results indicated that FB tibial implants migrated a significantly greater degree than MB implants. Within both groups, the majority of migration occurred within the first 3 months after surgery. Both groups displayed similar loss of BMD, which did not correlate to implant migration. OKS was significantly increased in both groups, with no significant between-group differences observed.