The thighs are concave when pressed, which may be cardiogenic edema, nephrogenic edema, endocrine metabolic edema or limited edema. 1. Cardiogenic edema: it is mainly caused by right heart failure, which increases hydrostatic pressure in the capillaries. It usually originates from the low-hanging area first, and then progresses to the thighs, which is concave; if lying down for a long period of time, it may appear in the thighs and lumbosacral area first. 2. Nephrogenic edema: it is edema caused by sodium retention and increase of extracellular fluid due to various factors. Thigh edema can be seen in nephrotic edema caused by nephrotic syndrome. 3. Endocrine metabolic edema: common causes include hypothyroidism, hyperthyroidism, Cushing’s syndrome, primary aldosteronism and so on. 4. Limited edema: often due to inflammation caused by infection, lymphatic reflux obstruction, varicose veins and so on. There are many reasons why thighs are concave when pressed, and you should go to the hospital as soon as possible to have a doctor make a diagnosis and treatment plan so as not to delay your condition.