In Asian women undergoing total knee arthroplasty, lower leg morphology in those with rheumatoid arthritis differed from those with osteoarthritis.

This retrospective, single-center study aimed to compare leg morphology between patients with rheumatoid arthritis (RA) and those with osteoarthritis (OA) undergoing total knee arthroplasty (TKA). We enrolled 70 RA and 327 OA female patients undergoing TKA. Hip-knee-ankle angle (HKA), femorotibial angle (FTA), valgus correction angle (VCA), and femoral/tibial bowing were measured using full-length radiographs. Femoral bowing of more than 3° or tibial bowing more than 2°, either laterally or medially, was considered substantial. Distribution of these results and the incidence of substantial bowing in RA and OA were compared. HKA, FTA, and VCA were significantly smaller in RA than those in OA. Femoral bowing was significantly smaller in RA (mean angle: 0.04° ± 3.1°) than that in OA (mean angle: 2.1° ± 3.6°) ( < .05). In almost half of the patients with RA (48.6%), femoral bowing occurred medially, whereas femoral bowing occurred laterally in approximately three quarters of OA patients (73.1%). Tibial bowing did not differ. The incidence of substantial femoral bowing was significantly lower in RA (27.1%) than that in OA (43.0%) ( < .05). RA patients undergoing TKA had different leg morphology than OA patients. These findings have implications for surgical planning.