Osteosarcoma: Symptoms, Stages, and Treatment

This page explains osteosarcoma, a bone cancer, for patients and families. It covers symptoms, staging, treatment, and when to get emergency care.

Osteosarcoma is a rare cancer. It starts in osteoblasts, the cells that build new bone. It most often grows in the long bones of the arm or leg. The bone just above or below the knee is the usual site. Osteosarcoma is most common in adolescents and young adults, though it can occur at any age.

Symptoms include pain in a bone or joint and swelling over a bone. Over half of people with osteosarcoma have it in a long bone near the knee. NCI lists these possible signs:

• Swelling over a bone or bony part of the body.
• Pain in a bone or joint, or in the arm when lifting.
• Stiffness in a joint.
• A limp or trouble walking.
• A bone that breaks for no known reason.

NCI says to check with a doctor if you or your child has any of these signs. They can also come from other conditions, so only tests can tell the cause.

Osteosarcoma does not use a traditional stage-by-number system. It is usually put into one of two groups:

• Localized means the cancer is still within the bone where it started. Nearby soft tissue may be involved.
• Metastatic means the cancer has spread to another part of the body. The lungs are the most common site, and sometimes other bones.

Treatment usually follows this pattern:

1. Chemotherapy first, to shrink the tumor and treat any cancer cells that may have already spread.
2. Surgery to remove the tumor. Many people can have limb-sparing surgery instead of amputation. The tumor is removed, and the bone is replaced with a graft from another part of the body or with an implant such as artificial bone. Amputation is usually done when all of the tumor cannot be removed with limb-sparing surgery.
3. More chemotherapy after surgery, to lower the chance the cancer will return.

Osteosarcoma is sometimes in or near the spine. A tumor pressing on the spinal cord is a medical emergency called spinal cord compression. Get emergency care right away for new back pain along with:

• Leg weakness or trouble walking.
• Numbness in the legs or lower body.
• New loss of control of urine or stool.

Quick treatment gives the best chance of preventing permanent nerve damage. This warning is general safety advice and was not re-checked against a source for this page.

• National Cancer Institute, Osteosarcoma and Undifferentiated Pleomorphic Sarcoma of Bone Treatment (PDQ) – Patient Version, accessed August 3, 2026.
• American Cancer Society, Bone Metastases, not re-opened on October 2, 2026; used only for the emergency warning.