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

Objectives: 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).Methods: 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.Results: 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°) (p < .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%) (p < .05).Conclusion: RA patients undergoing TKA had different leg morphology than OA patients. These findings have implications for surgical planning.