The study cohort will consist of 790 individuals identified from three Chicago-area medical centers, of whom 500 will have PAD. Participants will undergo a baseline and two annual follow-up visits. Pathophysiologic findings in the lower extremities refer to reduced muscle mass, reduced muscle quality, and reduced peripheral sensory and motor function. Quality of muscle tissue is defined as the ratio of muscle force to muscle mass. Muscle mass will be measured with Computed Tomography (CT). Peripheral nerve function will be determined using surface electroneurography (ENG). Lower extremity functional measures will consist of measures pertinent to functioning during daily living and include six minute walk distance, seven-day physical activity level (assessed by accelerometer), walking speed, balance tests, and lower extremity muscle power.