Bone and Joint Infections (Osteomyelitis and Septic Arthritis)

One out of every 5,000 children under the age of thirteen will be diagnosed with osteomyelitis, commonly known as a bone infection. Almost twice as many will be diagnosed with a septic arthritis, commonly known as a joint infection. These bone and joint infections occur much more commonly in children than in adults. The majority of cases occur in children under the age of five.

Causes of Bone Infection

Bacteria in the blood is very common in childhood. This can result from other infections, such as from the ear, nose, and throat, or it can be from simply brushing the teeth. For this bacteria to cause a bone infection, several things must occur

1. The bacteria must be strong enough to cause an infection
   
2. There must be a sufficient amount of bacteria in blood to cause an infection
3. The bacteria must be able to overload a person’s own immune system.  Most of the time, the immune system wins, and the bacteria is cleared from the blood – but not always.  Not if the other factors are quite significant.

   Bacteria reaches bone due to its rich blood supply. In children, blood flow through the bone is more abundant, and it is slower than adults. This is likely the reason children are at higher risk for developing a bone infection.

Causes for Joint Infection

The causes of joint infections are less well understood. Bacteria circulates in the blood, for reasons mentioned above. Most of the time, the immune system and the joint are able to get rid of the infection before it overwhelms the body, but again, if the bacteria are particularly strong and/or large in number, then it may overwhelm the joint and cause an infection. In addition, sometimes an infection from a bone can cross into a joint. This commonly occurs in four locations – the hip, shoulder, elbow, and ankle.

Diagnosis

Diagnosis of a bone or joint infection in children is not always straight-forward. Children will usually have fever and either a limp on the extremity affected, refusal to move the limb, or sometimes, refusal to walk at all. Most children are swollen and tender at the site of the infection, and the area may be warm. If a joint is infected, it may be extremely painful if the child attempts to move the joint. A combination of blood tests is helpful at making the diagnosis, and often, an MRI is necessary to help localize the exact location of the infection.

Treatment

Similar to other infections, antibiotics are the main treatment of these infections. If the infection involves a joint, then surgery is necessary to “clean out” the joint to prevent cartilage damage. If the infection involves the bone, surgery can also be necessary.

Antibiotics are initially administered through an IV, and once the infection shows significant improvement, often times, your physician will switch the antibiotics to ones taken by mouth. It is extremely important in the case of joint infections to begin physical therapy right away to help your child move his/her joint, as it can become permanently stiff very quickly.

Prognosis

If infections are treated promptly, often there are no consequences. However, infections can weaken bone, at least temporarily, and this puts your child at risk for fracture until the bone becomes strong again. Specifically for joint infections, sometimes the cartilage damage can be permanent and can lead to pain and future arthritis. Therefore, it is important for your child to continue seeing the doctor to help identify some of these potential problems early.