High functioning military transtibial amputees (TTAs) with well‐fitted state of the art
prosthetics have gait that is indistinguishable from healthy individuals, yet they are
more likely to develop knee osteoarthritis (OA) of their intact limbs. This contrasts
with the information at the knees of the amputated limbs that have been shown to
be at a significantly reduced risk of pain and OA. The hypothesis of this study is that
biomechanics can explain the difference in knee OA risk. Eleven military unilateral
TTAs and eleven matched healthy controls underwent gait analysis. Muscle forces
and joint contact forces at the knee were quantified using musculoskeletal modeling,
validated using electromyography measurements. Peak knee contact forces for the
intact limbs on both the medial and lateral compartments were significantly greater
than the healthy controls (P ≤ .006). Additionally, the intact limbs had greater peak
semimembranosus (P = .001) and gastrocnemius (P ≤ .001) muscle forces compared
to the controls. This study has for the first time provided robust evidence of increased
force on the non‐affected knees of high functioning TTAs that supports the
mechanically based hypothesis to explain the documented higher risk of knee OA in
this patient group. The results suggest several protentional strategies to mitigate
knee OA of the intact limbs, which may include the improvements of the prosthetic
foot control, socket design, and strengthening of the amputated muscles.