Peripheral Artery Disease (PAD): The pain in the calves and feet, especially upon waking and relieved by walking, is highly suggestive of intermittent claudication, a hallmark symptom of PAD. This condition is characterized by atherosclerosis of the peripheral arteries, leading to reduced blood flow to the muscles during exercise or activity.

Musculoskeletal Strain or Overuse: Morning pain that improves with activity could be related to musculoskeletal issues such as strain or overuse, particularly if the patient has recently increased physical activity or has a job that involves standing or walking for long periods.
Plantar Fasciitis: This condition causes pain in the heel and bottom of the foot, typically worse with the first steps in the morning and improving with activity. While it usually affects one foot, it can occur bilaterally.
Nighttime or Resting Peripheral Ischemia: Similar to PAD but occurs at rest, often due to more severe arterial disease. The pain can occur at night and be relieved by hanging the legs over the side of the bed or walking.

Deep Vein Thrombosis (DVT): Although DVT typically presents with unilateral symptoms, it's crucial not to miss this diagnosis due to its potential for severe complications like pulmonary embolism. Bilateral DVT, though less common, can occur.
Compartment Syndrome: A medical emergency that can cause severe pain, especially after exercise or at night, and can lead to permanent damage if not promptly treated.
Neoplastic or Metabolic Causes: Rarely, systemic diseases such as amyloidosis or certain types of cancer can cause peripheral neuropathy or vascular issues leading to similar symptoms.

Erythromelalgia: A disorder characterized by burning pain, heat, and redness in the hands and feet, which can be relieved by cooling or elevating the affected limbs.
Chronic Inflammatory Diseases: Conditions like rheumatoid arthritis or lupus can cause foot and calf pain, though these are typically accompanied by other systemic symptoms.
Neurological Disorders: Certain neurological conditions, such as peripheral neuropathy due to diabetes or vitamin deficiencies, can cause pain in the feet and calves, often with other neurological symptoms.