Conflicting findings exist regarding the association between obesity and functionality after total knee arthroplasty (TKA). We aimed to compare knee extensor mechanism function, knee function, and knee flexion range of motion between obese and nonobese patients who underwent simultaneous bilateral TKA. A total of 153 patients were divided into two groups as the obese (N = 99) and nonobese (N = 54) groups. The groups were compared for knee extensor mechanism function (chair-rise test), knee function (Hospital for Special Surgery [HSS] knee score), and knee flexion range of motion. The follow-up period was 2 years. In the chair-rise test, no statistically significant group-by-time interaction (χ2 (5) = 1.29, p = 0.93) or main effect of group (χ2 (1) = 0.02, p = 0.90) was found. For the HSS knee score, neither the group-by-time interaction (F (5, 728.17) = 0.17, p = 0.97) nor the main effect of group (F (1, 146.79) = 2.21, p = 0.14) was statistically significant. Regarding knee flexion range of motion, the group-by-time interaction was not statistically significant (F (5, 728.01) = 0.10, p = 0.99), whereas the main effect of group was statistically significant (F (1, 146.81) = 4.19, p = 0.04), with the obese group exhibiting lower knee flexion range of motion than the nonobese group. Obese and nonobese patients show similar improvements in knee extensor mechanism function, knee function, and knee flexion range of motion during the 2 years following simultaneous bilateral TKA. Obese patients have lower knee flexion range of motion compared with nonobese patients over the 2-year period after TKA. At the end of 2 years after TKA, both obese and nonobese patients achieve satisfactory results in all outcomes.

The study was approved by the Medical Research Ethics Committee of Ege University (decision no. 24-4T/56).

Received: 07 November 2025

Accepted after revision: 29 May 2026

Article published online:
11 June 2026

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