The pathophysiology of functional impairment in patients with lower extremity peripheral arterial disease (PAD) is not well understood. Although lower ankle brachial index (ABI) levels are associated with greater functional impairment, one study suggests that the ABI improves to a greater degree than functional impairment after lower extremity revascularization. A meta-analysis of exercise studies in intermittent claudication demonstrated no significant association between improved walking ability after exercise and change in calf blood flow or ABI. Thus, characteristics in addition to ABI appear to influence walking ability in PAD.