Intermittent Claudication: This condition, often associated with peripheral arterial disease (PAD), is characterized by leg pain that occurs during walking or exercise and is relieved by rest. Given the patient's age, atherosclerosis is a common underlying factor, making this diagnosis highly plausible.

Musculoskeletal Issues (e.g., Osteoarthritis): Age-related wear and tear on the joints can cause intermittent pain in the legs, especially with activity.
Neurogenic Claudication: This condition, often due to spinal stenosis, causes pain, weakness, or fatigue in the legs, calves, or buttocks that occurs with standing or walking and is relieved by sitting or leaning forward.
Diabetic Neuropathy: If the patient has diabetes, neuropathic pain could be a cause of intermittent leg pain, characterized by burning, tingling, or shooting pain.

Deep Vein Thrombosis (DVT): Although less common, DVT is a critical diagnosis to consider due to its potential for severe complications, such as pulmonary embolism. Risk factors include age, immobility, and recent surgery.
Acute Arterial Occlusion: Sudden onset of severe leg pain could indicate an acute arterial occlusion, which is a medical emergency requiring immediate intervention.
Infection (e.g., Cellulitis, Osteomyelitis): Infections can cause leg pain and are particularly concerning in elderly patients due to potential for rapid progression and severe consequences.

Chronic Compartment Syndrome: This condition, characterized by increased pressure within a muscle compartment, can cause pain with activity. It's less common but should be considered in the differential, especially if other diagnoses are ruled out.
Erythromelalgia: A rare disorder characterized by burning pain, heat, and redness in the hands and feet, which could potentially cause intermittent leg pain.
Peripheral Neuropathy due to Vitamin Deficiency: Deficiencies in vitamins like B12 can cause neuropathic pain, although this would be less common and typically associated with other systemic symptoms.