[Purpose] To evaluate the intra-and interobserver reliability of lower loading force measurements in a sitting. [Subjects] Thirteen patients after surgery for proximal femoral fractures in acute phase (mean age:80.8±6.3). [Methods] Two physical therapists as observers analyzed intra -and interobserver reliability using the interclass correlation coefficient (ICC). [Results] Analysis of intraobserver reliability showed ICC values of 0.813-0.911 on the operated sides and 0.960-0.963 on the non-operated sides. ICC of interobserver reliability was 0.830 on the operated sides and 0.956 on the non-operated sides, again showing good reproducibility. [Conclusion] We confirmed the reliability of lower limb loading force measurements in a sitting posture in patients after surgery for proximal femoral fractures.