There are several clinical causes of protruding knee bones: 1, tibial tuberosity osteochondritis, manifested as a protrusion of the tibial tuberosity in the anterior and inferior parts of the knee joint, mostly in adolescents, especially sports-loving adolescents, because the tibial tuberosity has not been completely ossified, while the patellar ligament is repeatedly stretched during activity, resulting in aggravation after exercise and reduction after rest. The diagnosis can be confirmed by radiographs, and can be improved by rest and physical therapy. 2. Osteomalacia, mostly seen in the elderly, is aggravated after activity and reduced after rest, especially when squatting or climbing stairs, and can be confirmed by radiographs. 3. Bone tumors, most commonly osteochondroma, occur in the tibia or the epiphysis of the femur, most of which are asymptomatic. Most of them are asymptomatic and require imaging tests such as X-rays or MRI of the knee joint and, if necessary, surgery.