An osteochondroma is an abnormal growth that appears near the end of a bone. The condition is benign and does not usually cause symptoms, though a large tumor may irritate joint tissue or constrict blood vessels and nerves. Depending on underlying genetic factors, a person may have a single osteochondroma near a major joint or several masses throughout the body. Asymptomatic tumors do not typically require medical care, but surgery is needed if a mass causes joint pain, numbness, or a bone fracture.
Most osteochondromas appear near growth plates, sections of tissue at the ends of bones that promote hardening of new bone cells. Tumors act much like growth plates, producing new cartilage and bone tissue that build up in a hard mass. Since bone growth is most active during adolescence, an osteochondroma is most likely to develop in a person between the ages of 10 and 18. A tumor rarely arises after the age of 30, though a childhood osteochondroma may not be detected until adulthood if it does not cause symptoms.
Doctors have identified several potential causes of osteochondromas. Single lesions typically arise after direct trauma to growth plates during periods of active bone development. A person who has multiple tumors usually has an underlying genetic condition, called hereditary multiple exostoses (HME), that was passed down from one or both parents. Abnormal growth plate activity related to HME can lead to the development of dozens or even hundreds of osteochondromas in a developing child or adolescent.
A large osteochondroma can cause pain and inflammation in the knee, hip, ankle, wrist, or another major body joint. If a tumor impedes on blood vessels or nerves, it can lead to clots, muscle weakness, and frequent episodes of tingling or numbness. Rarely, a growth can put enough pressure on the bone to cause a painful fracture. In most cases, however, osteochondromas do not become big enough to cause physical symptoms.
Asymptomatic osteochondromas often remain undetected until patients undergo x-rays for unrelated problems. When a tumor is discovered, a doctor usually performs a series of diagnostic imaging tests to study it carefully and check for additional lesions. A tissue sample may be extracted and analyzed to make sure it is not malignant. Treatment decisions are made based on the size, location, number, and symptoms of existing tumors.
Most patients do not need treatment for osteochondromas. Doctors simply suggest they schedule regular checkups to make sure the condition does not worsen. If a tumor causes pain and swelling, a patient may be referred to an orthopedic surgeon for further inspection. Surgery typically involves manually removing the tumor, mending healthy bone and cartilage, and ensuring that the growth plate itself is not damaged. Surgical procedures are relatively straightforward and have a very high success rate, and tumors are unlikely to reappear after they are removed.