Bone protrusion on the inside of the knee in children is not necessarily normal, it may be a normal bony protrusion or physiologic knee valgus, or it may be caused by rickets, osteochondroma and other diseases. On the inner side of the patella, there are a series of bony prominences such as the medial femoral condyle, the inner side of the tibial plateau, etc. Certain children may have a more prominent condition due to genetic factors, which are all normal bony prominences. Children can have physiological knee valgus after 2 years of age, which can be corrected with growth and development, but for those with more significant valgus, the later development generally can not be corrected at a later stage. From the viewpoint of bone structure, this kind of medial bone protrusion is normal. If the knee valgus is significant, we also need to be alert to whether it is rickets and other causes of pathologic knee valgus. Meanwhile, for children’s osteochondroma on the inner side of the knee, although the nature of osteochondroma is benign, it is an abnormal hyperplastic lesion for the normal bone structure of the knee joint, which is not a normal situation. Severe osteochondromas also require surgical removal. Therefore, children with protruding bones on the inner side of the knee should consult the hospital in time to clarify their situation.