There are many reasons for the thumping sound of the thigh root bone, such as physiological phenomenon, osteophytes, hip synovitis, old ligament injuries and so on. 1. Physiological phenomenon: many people may appear thumping sound when thigh root activities, especially in the lack of exercise, long-term sedentary people, mainly due to sudden changes in the pressure in the joint cavity caused by no other discomforts, and do not need to deal with. 2. Osteomalacia: Osteomalacia in middle-aged and elderly people, hyperplasia of the bone and the surrounding joint capsule ligament friction, will emit a popping sound, manifesting the thumping sound at the root of the thigh bone. 3. Hip synovitis: Hip synovitis will appear similar symptoms in the early stage, accompanied by severe pain in the hip joint and limited activities. 4. ligament old injury: ligament due to trauma, strenuous exercise and other factors injury, recovery, localized mechanization hyperplasia, activity and bony structure friction caused by popping, so there will be a thumping sound at the root of the thigh. There are many reasons for the thumping sound of the thigh root bone, it is recommended to go to the hospital to improve the examination and clarify the cause of the disease.