Myositis Ossificans

What is myositis ossificans?

Myositis ossificans (my-uh-SY-tuss uh-SIH-fuh-kanz) is when a bone forms inside your muscle or other soft tissue. Usually, myositis ossificans develops after a traumatic injury. Most often, it affects large muscles, such as in your arms or legs.

When bone forms where it shouldn’t, you may develop a painful, tender lump. Myositis ossificans that develops after an injury is the most common type of heterotopic ossification.

Who might get myositis ossificans?

Myositis ossificans is most common in young, active people and athletes of all levels. It is also more likely to occur in people who are paralyzed from the waist down (paraplegia), even if they haven’t had an injury that started the symptoms.

What are the types of myositis ossificans?

Doctors classify myositis ossificans into two types:

• Nonhereditary myositis ossificans: This type is the most common. It’s what people usually mean when they refer to myositis ossificans. It occurs after an injury, often in your thighs or arms. People may also use the terms myositis ossificans traumatica or myositis ossificans circumscripta.
• Myositis ossificans progressiva: People may use this older term when referring to fibrodysplasia ossificans progressiva (FOP). This type occurs because of a gene change (mutation).

What causes myositis ossificans?

When you are injured, your body immediately starts making new cells to heal itself. Nonhereditary myositis ossificans occurs when your body doesn’t make the right cells during the healing process. Instead of making muscle cells (fibroblasts), it creates new bone cells.

Myositis ossificans progressiva occurs because of a gene mutation. You may inherit this gene mutation from your parents. Or it may occur spontaneously (for no known reason).

What are the symptoms of myositis ossificans?

The most common sign of myositis ossificans is a large lump beneath your skin. In around 4 in 5 people, the bump forms in your arm or leg muscle. People with paraplegia are more likely to have lumps grow around their hips or knees.

The lump may be:

• Fast-growing.
• Painful.
• Swollen.
• Tender.
• Warm to the touch.

As the lump gets bigger, it may reduce your range of motion. You’re more likely to have reduced range of motion if the growth is near a joint.

How is myositis ossificans diagnosed?

To diagnose myositis ossificans, your healthcare provider examines you and asks you about symptoms. They may touch the bony lump to see if it hurts or is warm.

They may also use imaging scans such as a:

• CT scan.
• MRI.
• Positron emission tomography (PET) scan.
• Ultrasound.
• X-ray.

Your provider may also perform a biopsy by taking a small sample of tissue from the growth. A laboratory examines the tissue to look for signs of myositis ossificans or other conditions with similar symptoms.

How is myositis ossificans treated?

Often, myositis ossificans traumatica goes away by treating it at home. For all types of myositis ossificans, you may start with nonsurgical treatments, such as:

• Icing the bump.
• Limiting your activity to rest the area.
• Stretching gently.
• Taking nonsteroidal anti-inflammatory drugs (NSAIDs).
• Using an elastic bandage to decrease swelling.

Your provider may also recommend physical therapy. Physical therapy helps you increase strength, flexibility and range of motion.

In severe cases, your provider may recommend surgery to remove the bony growth. Usually, you only need surgery if you have severe pain or limited function that doesn’t improve with nonsurgical treatment.

How can I reduce my risk of myositis ossificans?

There’s no guaranteed way to prevent myositis ossificans. But you can reduce your risk of nonhereditary myositis ossificans by treating injuries properly, especially if you have a severe bruise or swelling. Immediately after injury, use the RICE method. RICE stands for:

• Rest.
• Ice.
• Compression.
• Elevation.

Reducing your risk of injury may also reduce your risk for myositis ossificans. Proper conditioning, stretching and adequate rest are all crucial for injury prevention.

What is the outlook for myositis ossificans?

Usually, if myositis ossificans develops after an injury, it goes away with nonsurgical treatment. You may have limited range of motion or lingering stiffness for several months after treatment.

There’s no cure for myositis ossificans progressiva. This severe condition causes symptoms that progress throughout your life and may lead to a shorter lifespan.

What else should I ask my doctor?

You may also want to ask your healthcare provider:

• What is the most likely cause of myositis ossificans?
• What types of myositis ossificans do I have?
• What are the treatment options?
• What could happen if I don’t get treatment for myositis ossificans?
• What are the chances that I’ll pass myositis ossificans progressiva to my child?

What can I do to prevent myositis ossificans traumatica from developing again?

What conditions have similar symptoms to myositis ossificans?

Some conditions can also cause painful lumps in your soft tissue. Your healthcare provider gives you tests during myositis ossificans diagnosis to rule out other conditions with similar symptoms, such as:

• Nodular fasciitis.
• Osteosarcoma.

A note from Cleveland Clinic

Myositis ossificans occurs when bone forms where it shouldn’t, usually in your muscles or other soft tissues. Usually, myositis ossificans develops after a traumatic injury. Rarer hereditary types of myositis ossificans cause more severe symptoms. There’s no cure for these types of myositis ossificans. Doctors typically treat myositis ossificans traumatica with nonsurgical methods. For most people, this type of myositis ossificans goes away after several weeks or months.