The most common causes of thigh soreness are over-exercise, lumbar disc herniation, sciatica, and thromboembolic vasculitis, etc. If the symptoms persist, it is recommended that you seek medical attention in a timely manner. 1. Excessive exercise: If you play strenuous sports, such as long-distance running or playing soccer, it is easy to cause the accumulation of lactic acid in the muscles of the thighs, which in turn causes soreness and swelling of the thighs. 2. Herniated lumbar discs: Herniated lumbar discs compress the surrounding nerves, which can easily cause numbness and soreness in the thighs. 3. Sciatica: irritation or pressure on the sciatic nerve can easily cause numbness and soreness in the thighs. 4. Thromboembolic vasculitis: this is a chronic, occlusive inflammatory disease that occurs in the blood vessels of the lower limbs, which can cause soreness and pain in the thighs and may be accompanied by pale skin color. Causes of thigh soreness and swelling of more reasons, but also with lumbar spinal stenosis, tumors, osteoarthritis, bone fractures, muscle strain and other diseases, it is recommended to go to the hospital in a timely manner by the doctor to identify the cause of the disease, targeted treatment.