Altering prosthetic alignment does not affect hip and low back joint loading during sit-to-stand in people with a transtibial amputation

People with a transtibial amputation (TTA) have greater prevalence of low back and hip joint pain compared to the general population. Altered movement, loading patterns, and neuromuscular activation during daily tasks like sit-to-stand likely contribute to these high rates of pain. In addition, muscle activation, ground reaction forces, and trunk range of motion can be affected by prosthetic alignment during sit-to-stand. However, it is unclear how prosthetic alignment affects joint contact forces during this task. The purpose of this study was to investigate the effect of prosthetic alignment on hip and low-back joint loading in people with TTA during sit-to-stand. Kinematics, ground reaction forces, and muscle activity data were collected from 10 people with TTA and 10 age- and sex- matched individuals without limb loss during five self-paced sit-to-stand trials. Participants with TTA completed the sit-to-stand task with their prescribed alignment and six altered alignment conditions (±10 mm anterior/posterior, medial/lateral, and ± 20 mm short/tall). A musculoskeletal model was used to calculate hip and L4-L5 joint loading. There were no differences in hip or L4-L5 joint loading between alignments. Participants with TTA had a greater peak hip joint contact force on the intact side hip compared to the amputated side hip across all alignments. Participants with TTA had greater L4-L5 joint contact force compared to those without amputation. While prosthetic alignment did not affect joint loading during sit-to-stand, future work on additional dynamic tasks is needed to better understand the potential role of prosthetic alignment on joint loading.