Subcutaneous bumps on the inner side of the thigh fossa may be caused by lymphadenitis, epidermoid cyst, lipoma and other diseases. 1. Lymphadenitis: If the skin and soft tissues of the lower limbs are infected, it can lead to the enlargement and pain of the neighboring lymph nodes, resulting in the appearance of smooth and tough subcutaneous lumps on the inner side of the thigh fossa, which can be accompanied by tenderness. 2. Epidermoid cysts: the cause of the disease is mostly related to skin injury, embryonic ectopic and other factors, the patient’s skin will appear dome-shaped elevated skin swelling, the disease can be seen in all parts of the body, and some patients may grow lumps on the inner side of the thigh fossa. 3. Lipoma: the cause of the disease is unknown, may be related to genetic factors, mainly manifested as a single or multiple lumps under the skin, commonly found in the neck and shoulders, buttocks, thighs and other places. There are many reasons that lead to the growth of lumps under the skin on the inner side of the thighs, and it is recommended that patients go to the hospital to get a clear cause of the disease.