Peripheral Artery Disease (PAD): This condition is characterized by the narrowing or blockage of the blood vessels outside of the heart, leading to reduced blood flow to the limbs. The symptoms of PAD, such as intermittent claudication (pain in the legs or arms during exercise), match the description of leg cramps that occur during rest and worsen with walking.

Muscle Strain or Overuse: Repeated strain on the muscles in the thigh can lead to cramping, especially if the individual has recently increased their physical activity level or has poor muscle conditioning.
Electrolyte Imbalance: Abnormal levels of electrolytes such as potassium, sodium, or calcium can cause muscle cramps. This could be due to various reasons including dehydration, certain medications, or underlying kidney or hormonal disorders.
Neurological Conditions: Conditions like neuropathy (nerve damage) can cause pain, numbness, or cramping in the legs, which might worsen with activity.

Deep Vein Thrombosis (DVT): Although less common, DVT can cause leg pain that worsens with walking. It's crucial to consider this diagnosis due to its potential for severe complications, such as pulmonary embolism.
Compartment Syndrome: This is a condition where pressure within the muscles builds to dangerous levels, decreasing blood flow and potentially leading to nerve and muscle damage. It's a medical emergency that requires immediate attention.

Amyloidosis: A group of diseases that result from the abnormal accumulation of amyloid proteins in various tissues, which can lead to neuropathy and muscle cramps among other symptoms.
Sickle Cell Disease: A genetic disorder that affects hemoglobin production, leading to abnormal red blood cells. These cells can get stuck in small blood vessels, causing pain episodes, including leg pain.
Vasculitis: Inflammation of the blood vessels, which can lead to a reduction in blood flow and cause symptoms similar to those described.