When cancer spreads from a primary site to the bones, the bone tumors are called bone metastases, or bone mets. This can happen with any type of cancer but it occurs more frequently in breast, lung, or prostate cancer.

There are two types of bone cells: osteoblasts and osteoclasts. Osteoblasts break down bones and osteoclasts build new bones. When cancer spreads to your bones, it changes how these cells work. It makes your bones more fragile, increasing the risk of fractures.

Bone metastases can be very painful. The pain is from structural damage to the bones and inflammation caused by cancer cells. Sometimes the pain is related to a bone fracture.

Bone metastases can’t be cured, but treatments can help prevent further spread of cancer and alleviate symptoms like bone pain.

Bone pain is the most common symptom of metastatic bone cancer. It may be the first sign of metastases. Bone metastases are most likely to occur in the spine, ribs, hips, upper leg, upper arm, and skull.

Sometimes the pain can be sharp. Other times it’s a dull ache. There may also be some swelling at the site of the pain. Many people find the pain can be worse at night.

In earlier stages, the pain is more likely to come and go. As cancer grows, pain may become more constant. Depending on the site of the bone cancer, movement can increase the pain. Sometimes the pain persists no matter what you’re doing or what position you’re in.

Bone cancer pain can be caused by:

  • inflammation from the cancer cells
  • changes in bone structure
  • a bone fracture

When cancer cells start growing in bones, they can cause a lot of damage. The affected bones may become very fragile. Even normal daily movements can cause bones to fracture or break.

The most common sites of bone fractures are the arms, legs, or back. Sudden intense pain can be a sign of a broken bone. If this happens, it’s important to seek medical attention.

Symptoms of bone metastases can vary depending on how much the cancer has spread and which bones are affected. Some common signs and symptoms include:

  • Bone fractures. Damage to bones makes them weak and more prone to fractures or bone breaks. Sometimes this is the first sign that cancer has spread to the bones.
  • Bone pain. This is the most common symptom of bone metastases. The pain may be dull and achy or sharp with a sudden onset.
  • Nerve issues. If a bone tumor is pressing on the spinal cord, it can affect nerve function. Known as spinal cord compression, this can lead to symptoms like tingling, weakness, or numbness in the legs or arms. Left untreated, it can lead to paralysis.
  • High calcium levels in the blood. Also known as hypercalcemia, this can lead to symptoms like constipation, extreme thirst, low appetite, or confusion. It can typically be found through blood work.
  • Anemia. When bones are affected, it can reduce the number of blood cells created by bone marrow. This lowers red blood cells in the blood, known as anemia.

If you live with cancer, your care team will monitor any changes in your health. It’s important to be aware of any signs that may indicate that your cancer has spread to the bones. It’s always best to catch bone mets early to help slow the spread.

At first, the pain from bone mets may come and go. As cancer grows or spreads, the pain may become more constant. Many people find pain gets worse at night and can interrupt sleep.

Pain levels can vary depending on the cause and location. If the pain is due to structural changes in the bones, you may experience pain when you use those joints. It may also improve with rest. But as things progress, you may start to feel pain even when you’re not moving around.

It’s thought that if you experience increased pain when moving a certain joint, it may be at greater risk of fracture. But there’s no direct connection between severity of pain and fracture risk.

Sudden and intense pain can be due to a fracture or bone break. Cancer can make bones very weak and prone to fracture, even with normal daily activities.

In many cases, bone pain is the first sign that cancer has spread to the bones. If you’re living with cancer and you start to experience bone pain, get it checked out.

If the bone cancer is pressing on the spinal cord, you may also experience nerve problems. This can cause difficulties with movement and mobility. It may also affect bladder and bowel function. If you experience these symptoms, be sure to talk to your doctor.

It’s best to catch bone mets early to help prevent or slow the spread to the bones. You may have regular blood work to monitor red blood cell levels and blood calcium levels. Low red blood cell count or high blood calcium levels can be early signs of bone metastases.

In advanced stages, cancer may spread to the bones. When this happens, it’s called metastatic bone cancer. The resulting bone tumors are called bone metastases, or bone mets.

The telltale symptom of bone mets is bone pain. The cancer can also weaken bones and lead to an increased risk of fractures or bone breaks.

It’s always best to catch bone metastases early. Be sure to talk with your cancer care team if you experience bone pain or notice any other changes to your health.