The exostosis either becomes a spur, pointing back towards middle of the bone, or is filled in, becoming a lump close to the end. Sometimes the lump is rather irregular but no one knows why. One of the most common places to develop an exostosis is around the knee, an area of maximum growth. They are also common at the shoulder, the wrist and on the ribs. You don't usually get them on your head which is a different type of bone.
Lumps usually stop growing at the end of childhood.
In contrast, a few people develop many exostoses, perhaps even hundreds. Other names for HME include Multiple Osteochondromata , Osteochondromatosis , Diaphyseal Aclasis and Familial Bony Spurs . These all refer to the same condition. Although you usually inherit HME from one of your parents, it can sometimes develop unexpectedly. Boys and girls have an equal chance of being affected but there can be quite big variations within a family, some of the affected children developing many lumps and others only a few.