The protruding bone on the lateral side of the knee involves a variety of possibilities such as congenital dysplasia, fracture, osteophyte, and aseptic inflammation. 1. Congenital dysplasia: commonly caused by malnutrition, improper sitting posture, etc., which does not cause discomfort. 2. Fracture: The bone on the outside of the knee protrudes out due to car accidents, sports, etc., and there are symptoms such as pain, joint swelling, and limitation of extension and flexion. 3. Osteomalacia: caused by degenerative joint disease, infection, etc., manifested by protruding bones on the outside of the knee, friction sound from the joint when moving, and persistent pain. 4. Aseptic inflammation: such as osteoarthritis, tibial tuberosity epiphysitis or gouty arthritis, etc., which results in protruding of the lateral knee bone due to joint effusion, gouty stones or joint deformity, etc. If the protruding lateral knee bone is accompanied by obvious symptoms, it may cause pain. If the protruding lateral knee bone is accompanied by obvious pain, walking limitation and other symptoms, go to the regular medical institutions to find out the cause of the disease.