Chronic Venous Insufficiency (CVI): This condition is characterized by the veins having problems returning blood from the legs to the heart due to valve issues or blockage, leading to edema, tenderness, and potentially skin changes. It's a common cause of bilateral leg symptoms.

Heart Failure: Edema in both legs can be a sign of heart failure, where the heart is not pumping efficiently, leading to fluid buildup in the body, particularly in the lower extremities.
Kidney Disease: Conditions like nephrotic syndrome can cause significant protein loss in the urine, leading to hypoalbuminemia, which in turn causes fluid to leak out of blood vessels, resulting in edema.
Liver Cirrhosis: Cirrhosis can lead to hypoalbuminemia and also cause fluid retention due to portal hypertension, resulting in edema.
Deep Vein Thrombosis (DVT): Although DVT typically presents unilaterally, it can occasionally present bilaterally, causing tenderness and edema in both legs.

Lymphoma or Other Malignancies: Certain cancers can cause lymphedema or venous obstruction, leading to edema and tenderness. Early detection is crucial for treatment and prognosis.
Abdominal Aortic Aneurysm: A large aneurysm can compress the inferior vena cava or iliac veins, leading to bilateral leg edema and tenderness.
Nephrotic Syndrome: Due to its potential for significant morbidity if not treated promptly, it's crucial to consider this diagnosis in patients with bilateral leg edema.

Lipedema: A chronic condition characterized by the abnormal growth of fat cells in the legs, leading to swelling and tenderness. It's often mistaken for simple obesity or lymphedema.
Fabry Disease: A genetic disorder that can lead to the accumulation of a particular type of fat in the body's cells, affecting many parts of the body including causing pain and swelling in the legs.
Sarcoidosis: A disease characterized by the growth of granulomas (inflammatory cells) in various parts of the body, which can occasionally cause leg swelling and tenderness.