Periostitis is a medical condition that involves inflammation, tenderness, and swelling around one or more bones. Most bones in the body are lined with a layer of connective tissue called periosteum, which provides protection and secures muscle fibers to bone tissue. Periostitis occurs when a layer of periosteum is damaged due to an injury, severe infection, autoimmune disorder, or cancerous condition. Depending on the underlying cause, periostitis can cause acute pain in an isolated area of the body or widespread, chronic aches.

The most common cause of periostitis is injury from direct trauma to a bone or overuse of a particular body part. Athletes and casual runners are at risk of developing periosteum inflammation in their lower legs, a condition called shin splints. The frequent pressure put on the shins from running, stopping, jumping, and turning gradually irritates the periosteum surrounding the bones, and in some cases the connective tissue can tear. Improper running technique can exacerbate the problem, and shin splints can become debilitating.

Periostitis can also arise as a complication of a chronic infection, such as syphilis or an autoimmune disorder. In an inherited condition called primary hypertrophic osteoarthropathy, the immune system releases chemicals that cause inflammatory responses in periosteum at many different bone sites, including the collarbone, femur, and humerus. As a result, the connective tissue becomes inflamed and swollen. With the periosteum damaged, new bone forms underneath that causes painful protrusions and further irritates the connective tissue. Leukemia, a blood and bone marrow cancer, may also cause periostitis in the late stages of the cancer.

A doctor can diagnose periostitis and look for underlying causes by asking about symptoms, evaluating the physical appearance of affected body parts, and taking x-rays of bones. Blood tests may be performed if an autoimmune disorder or infection is suspected. If diagnostic tests are inconclusive, a sample of bone and periosteum tissue might be collected and analyzed to check for signs of cancer.

Doctors usually focus treatment efforts on eliminating the underlying cause of symptoms. In the case of shin splints or other injury-related forms of periostitis, patients are usually instructed to get rest, ice their sore bones, and take anti-inflammatory medications. Shins usually start feeling better after about a month of rest, and an individual can gradually increase his or her activity level to rebuild strength. Antibiotics, antivirals, or immunosuppressant drugs may be needed to treat other causes. Surgery to remove or repair damaged tissue may be necessary if the condition causes debilitating pain or bone fractures.