Introduction: People with transtibial amputation often suffer musculoskeletal deformities in the form of knee osteoarthritis or osteophytosis due to asymmetric movement patterns and often complain of associated symptoms. Therefore, this study aims to evaluate the sagittal kinematics of the intact and residual knee in the use of Running-Specific Prostheses (RSP), which are increasing in popularity and use among amputees.

Materials and Methods: Participants will be video recorded in the sagittal plane to convert knee flexion motion into angles for the amputee and intact knee and to make measurements using the software's virtual goniometer. Recordings will be taken under the following two conditions: 1) walking at a self-selected walking speed with a Daily Use Prosthesis (DUP); 2) Slow running with RSP. The peak flexion during the swing phase and the initial flexion during the first contact of the stance phase will be recorded as angles in both conditions.

Inclusion Criteria:

• body mass index below 30 kg/m2,
• Having unilateral transtibial amputation,
• Being at K4 functional level,
• Having an existing running blade,
• Being able to use RSP integrating it into their DUP,
• Having no self-reported problems with the residual limb or prosthesis, pain or skin lesions,
• Being active recreational runners (at least once a week) for at least 1 and up to 3 months without injury.

Exclusion Criteria:

• Having a history of knee surgery or contracture in the intact/amputee knee.

Unilateral transtibial amputee at K4 functional level