• Functional Performance: 6-minute walk performance [ Time Frame: Baseline, 12 months, 24 months ] [ Designated as safety issue: No ]
  
• MRI: Mean Plaque Volume [ Time Frame: Baseline, 24 months ] [ Designated as safety issue: No ]
  

• Four meter walking velocity (usual pace), four meter walking velocity (fastest pace), SPPB [ Time Frame: Baseline, 12 months, 24 months ] [ Designated as safety issue: No ]
  
• MRI: maximum plaque volume, external remodeling, mean percent lumen reduction, maximum percent lumen reduction [ Time Frame: Baseline, 24 months ] [ Designated as safety issue: No ]
  

Plaque build-up caused by atherosclerosis increases the risk of blood clots, heart attack, and stroke. Blockages of plaque can occur in different areas of the body. PAD, a circulatory disorder in which blockages occur in the peripheral arteries, is one manifestation of atherosclerosis. Individuals with PAD experience reduced blood flow to the legs, which may cause leg pain while walking. This study will use MRI techniques to examine how characteristics of plaque build-up in the leg arteries change over time and how this change affects function, walking ability, leg strength, and balance in people with PAD. Results from this study may be used to shape future research studies that will attempt to identify more effective treatments for people with PAD.

This study will enroll people with PAD, as well as a smaller control group of people who do not have PAD. At an initial study visit, study researchers will interview participants to collect information about their medical history, daily activity level, walking ability, and mental functioning. Blood collection and a leg MRI will occur. Also, blood flow to the legs will be measured by comparing blood pressure measurements in the arms and legs. Leg function will be measured through a series of timed walks, leg strength exercises, and muscle power exercises. Questionnaires to assess participants' medical history will be completed by each participant's primary care doctor, and study researchers will review participants' medical records.

Participants with knee pain will have a knee x-ray, and participants may wear a small device called an accelerometer for 1 week to monitor physical activity levels. During the second and third study visits, occurring at one and two year follow-up, blood flow, leg function, and leg strength will be measured. If participants cannot attend either study visit, researchers may visit participants at their home or conduct an interview over the phone.

Study researchers may contact participants by phone once or twice a year for follow-up.