Amputee gait produces periodic occlusion of residual limb blood vessels. During the stance phase of gait, body weight cause the prosthesis to compresses the soft tissue of the residual limb and occlude blood flow. This occlusion can be relieved during swing phase, but may depend on type of prosthesis. The purpose of the proposed research is to: (1) discover the range of tissue oxygenation in the intact and residual lower limbs of dysvascular amputees during gait and (2) to learn which of five different prosthetic limb systems provides greater tissue oxygenation.

The amount of oxygen in residual limb tissue is an important health status indicator; resistance to infection, promotion of wound healing, production of collagen, and epithelialization all correlate with higher oxygen levels. Unfortunately, simply donning a lower limb prosthesis may limit circulation and reduce the level of tissue oxygenation. This reduction may be compounded by the biomechanical forces of gait. The compressive loads of the body's weight during stance and the inertial loads of the prosthesis during swing may further occlude circulation, albeit by different mechanisms.

For the dysvascular lower limb amputee, the choice of prosthetic socket and suspension system may impact the overall health of their residual limb and wound healing capacity. An inappropriate choice may lead to skin irritation, tissue breakdown, discomfort, and reduced mobility. For these patients, any component that reduces tissue oxygenation is a significant problem because compromised circulation can forestall wound healing.

The objective of the proposed research is to use photo-oximetry to discover which of five different prosthetic limb systems results in higher residual limb tissue oxygenation during both rest and gait. This experiment will enable evidence-based decision making on this clinically relevant problem. Using a prospective, randomized cross-over experimental design and the investigators' photo-oximetry system, the investigators will measure and compare the tissue oxygenation along the medial and lateral surfaces (3 sites each) of the residual limb during rest and walking.

Inclusion Criteria:

All subjects must meet the following inclusion criteria:

• unilateral transtibial amputee of diabetic etiology between the ages of 18 and 70,
• have been fit with a prosthesis and have used a prosthesis for at least one year,
• wear the prosthesis at least 4 hours per day,
• ambulate without upper extremity aids, and
• have no history of injurious falls within the previous six months.

Exclusion Criteria:

Subjects will be excluded if:

• they have a significant lower extremity pain condition, musculoskeletal disorder, or neurological deficit that interferes with their ability to pursue typical daily activities or alters their gait characteristics or
• their residual limb is ulcerated.