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What is myositis ossificans?

Myositis ossificans occurs when bone forms inside a bruised muscle. When a muscle heals from trauma, calcium deposits can form a hard lump inside the tissue, especially if that muscle has been repeatedly bruised in the past.

Myositis ossificans most commonly affects male athletes between the ages of 13 and 35, particularly those who play contact sports, such as football, ice hockey, soccer, lacrosse, or rugby. It can also affect people with paraplegia.

While the condition can be painful and cause temporary loss of strength and range of motion, most cases of myositis ossificans resolve with rest and conservative treatment.

Myositis ossificans is not a tumor. While the growing lump, pain, and inflammation can mimic a tumor of the soft tissues, this is a reactive process to trauma and not a tumor.

What are the types of myositis ossificans in children, adolescents, and young adults?

  • Nonhereditary myositis ossificans, the most common type, is often the result of a sports injury or other trauma.
  • Myositis ossificans progressiva, also known as fibrodysplasia ossificans progressiva, is caused by a rare gene mutation. This type of myositis ossificans affects about one in 1 million people worldwide. Rather than resolving, symptoms usually become more severe over time.

Symptoms & Causes

What are the symptoms of myositis ossificans?

Most cases of myositis ossificans in athletes occur in the large muscles of the thigh or upper arm. Rather than healing, the bruised muscle becomes increasingly painful. The athlete may notice a hard lump in the area two to four weeks after the initial injury.

In people with paraplegia, myositis ossificans tends to develop around the knees or hips, often spontaneously rather than in response to an injury.

Symptoms include:

  • Persistent pain and loss of strength and range of motion
  • Fast-growing lump inside the muscle
  • Tender and warm to the touch

What causes myositis ossificans?

The most common type of myositis ossificans (nonhereditary myositis ossificans) occurs when the body produces bone cells instead of muscle cells in response to injury or trauma.

Several factors can increase an athlete’s risk of myositis ossificans:

  • Repetitive trauma to the same area
  • Not taking measures to reduce muscle inflammation after an injury through rest, icing, or compression
  • Returning to sport before a bruised muscle has fully healed

Myositis ossificans progressiva, the rare type of myositis ossificans, is caused by a gene mutation. In most cases, the mutation occurs for no known reason. In most cases, the condition is not passed down from parent to child.

Diagnosis & Treatments

How is myositis ossificans diagnosed?

At Boston Children’s Hospital, diagnosing myositis ossificans begins with a clinical evaluation and typically includes medical imaging.

  • A member of our orthopedic and sports medicine team will ask about your child’s injury, when it happened, and how the symptoms progressed.
  • We’ll examine the injured area, assess your child’s strength and flexibility, and gently press on the lump to see if it is warm or painful to the touch.
  • We may use tests such as X-ray, ultrasound, CT scan, or MRI to get a closer look at the lump and identify any bone material inside your child’s muscle.

How is myositis ossificans treated?

In most cases, if the bruised muscle has time to heal without further trauma, myositis ossificans goes away with minimal treatment.

Our sports medicine or orthopedic specialists will monitor your child over time to be sure the bony tissue breaks down and is reabsorbed in the body. We may recommend physical therapy to help your child safely regain muscle strength, flexibility, and range of motion.

To relieve pain and promote healing, we recommend these home remedies:

  • Rest: Avoid stressing the muscle
  • Ice: Ice the area for 15 to 20 minutes at a time
  • Compression: Wrap your child’s injured arm or leg in an elastic bandage to reduce swelling
  • Elevation: Prop the injured limb on pillows so it’s higher than your child’s heart

It’s important not to stretch the muscle until your child’s doctor says it’s safe to do so. Aggressive stretching too soon can cause more muscle trauma and attract more calcium deposits to the area.

While surgery is rarely necessary to treat myositis ossificans, we may recommend removing the lump surgically if your child is in severe pain or their symptoms don’t improve with conservative treatment.

How soon can my child return to sports after myositis ossificans?

Myositis ossificans can take a year to fully resolve, but your child may be able return to light exercise within two to three months and some vigorous activity by six months. We will continue to monitor your child’s recovery and let you know when your child can safely return to sports.

How we care for myositis ossificans at Boston Children’s Hospital

Boston Children’s Orthopedics and Sports Medicine Department provides patient-centered care for a wide range of pediatric conditions, including myositis ossificans. Our team is made up of experts in child and adolescent growth patterns and treatments that promote optimal recovery.

We understand the essential role sports play in many of our patients’ lives and work with our patients to help them return to sports stronger and healthier than ever.

To that end, we take a non-surgical approach to care whenever possible. If an injury requires surgery, we look for the least invasive options and practice pain management in ways that minimizes our patients’ exposure to anesthesia and promotes faster recoveries.