Many Service members (SM) with limb loss have achieved desired outcomes using conventional prosthetic sockets; in some cases, up to and including return to duty/re-deployment. However, certain characteristics (e.g., short residual limb, skin ulceration, heterotopic ossification) can result in substantial discomfort/pain, limitations in function, and/or device abandonment. Osseointegration (OI) aims to mitigate such complications via direct skeletal attachment of the prosthetic device and, thus, has the potential to vastly improve functional outcomes and quality of life. To compliment traditional surgical-based outcomes (i.e., those focused on the implant/abutment, soft tissue management, infection mitigation), all patients within the Department of Defense (DoD) OI Program also complete a comprehensive battery of outcomes assessments, throughout the continuum of care (i.e., before, and 3, 6, 12, and 24 months after OI), and spanning the broad domains of function, including traditional clinical-based assessments, quality and efficiency of gait/movement (biomechanics), imaging (whole-body and implant-site composition), and patient-reported outcomes (e.g., pain, quality of life, device satisfaction). Here, we report preliminary results from the functional and biomechanical domains for a subset of SM with transfemoral (TF) limb loss, before and 12-months after OI.