Osteomyelitis / Septic arthritis

Paediatric – Osteomyelitis / Septic Arthritis

What is Osteomyelitis?

Osteomyelitis is an infection of the bone. It normally affects the long bones of the body; however, it can affect any bone.

What is Septic Arthritis?

Septic arthritis is an infection of any joint and is an orthopaedic emergency. It most commonly affects the hip or knee joint, however it can affect any joint in the body.


Infection of the bone (Osteomyelitis) or a joint (Septic arthritis) is caused by a variety of bacteria or occasionally fungus. The bugs infect the bone or joint and can destroy the cartilage, bone and surrounding soft tissue.

The most common bacteria include:

Staphylococcus Aureus,
Escherichia Coli,
Haemophilus Influenzae

How do children contract this infection?

One of the most common ways for the infection to occur is from spread of the bacteria in the blood stream to the bone or joint. Infection can enter the blood stream due to a number of common conditions such as ear, throat or urinary tract infections.

Infection can also occur less commonly as a result of an injury or cut to the skin near a bone or joint.

The presence of infection in the bone (osteomyelitis) can sometimes spread to a nearby joint and cause infection in that joint (septic arthritis).

Often the source of the infection is never found.


Premature babies and children with medical conditions that affect the immune system are most at risk. However it can also occur in children with no risk factors.


The most common symptoms include:

Pain in the joint or bone involved

Not willing to walk, weight bear or use the affected limb
Generally unwell, not eating, irritable
Recent infection e.g. Ear, throat or urinary tract infection

Alternative diagnosis

Transient synovitis

Trauma or injury
Skin infection (cellulitis)


The doctor will initially perform simple observations of the child including:

Heart rate
Blood pressure
Oxygen level
Breathing rate

The area affected can be red and inflamed.

The child will be extremely irritable on any movement of the affected limb or joint. Often in cases of Septic arthritis of the hip the child will hold the limb in a flexed position.

The doctor will assess whether or not the child is able to walk.


Blood tests will usually be performed to look for signs of infection. These include:

White Cell Count
C Reactive Protein (CRP)
Erythrocyte Sedimentation Rate (ESR)
Blood Cultures

An X-ray of the affected limb or joint will be taken

Often X-rays are not sufficient on their own to provide the diagnosis so more advanced imaging is needed.

For Osteomyelitis an MRI is often the imaging modality of choice. It is a safe form of imaging and provides no radiation.

If Septic arthritis is suspected an Ultrasound test may be carried out. The ultrasound can show whether or not there is a collection of fluid in the joint, which may indicate infection.

If the child has symptoms and examination findings of Septic arthritis, they are given a general anaesthetic and a sample of fluid is taken from the involved joint and analysed for infection. If infection or pus is found, the joint must be opened and washed out in theatre immediately.


Treatment of Osteomyelitis and Septic arthritis is different, however the two can occur together.


The main treatment of osteomyelitis is intravenous antibiotics. This is often for a prolonged period of at least 6 weeks. This can necessitate staying in hospital for the initial period of the infection, however often the antibiotics can be administered at home.

Children have to be monitored to ensure the treatment is working with regular visits and blood tests.

Occasionally if antibiotics alone are not sufficient to fight the infection, surgical removal of the infection is required. This involves opening up the bone involved and removing the infected bone material.

Septic arthritis

Septic arthritis is an orthopaedic emergency. The only treatment option is to surgically open the joint (arthrotomy) and wash out the infection in the joint. Samples of the infection are also taken at the time of surgery and sent for analysis. This provides important information to insure the most effective combination of antibiotics can be given. Intravenous antibiotics are usually required for a prolonged period, often up to 6 weeks.  


The outcome depends on how quickly the condition is diagnosed and treated. It is therefore important that any child that develops any of the above symptoms is assessed by an appropriately qualified medical practitioner such as a GP or brought directly to the Emergency Department. Delayed diagnosis can lead to worse outcomes.

Septic arthritis can cause destruction of the cartilage within a joint and this can lead to post infection arthritis in that joint.

With the advent of modern antibiotics, mortality is low and less than 1%.

Last reviewed: September 2016

IITOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the IITOS "Find an Orthopaedist" section on this website.